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Fermiology of Chiral Cadmium Diarsenide CdAs2, a Candidate for Hosting Kramers–Weyl Fermions

  • Federico Mazzola
    Federico Mazzola
    Istituto Officina dei Materiali (IOM)−CNR, Laboratorio TASC, Area Science Park, S.S.14, km 163.5, I-34149 Trieste, Italy
    Department of Molecular Sciences and Nanosystems, Ca’ Foscari University of Venice, I-30172 Venice, Italy
    More by Federico Mazzola
  • , 
  • Yanxue Zhang
    Yanxue Zhang
    Key Laboratory of Materials Modification by Laser, Ion and Electron Beams, Ministry of Education, School of Physics, Dalian University of Technology, Dalian 116024, China
    More by Yanxue Zhang
  • , 
  • Natalia Olszowska
    Natalia Olszowska
    National Synchrotron Radiation Centre SOLARIS, Jagiellonian University, Czerwone Maki 98, PL-30392 Kraków, Poland
    More by Natalia Olszowska
  • , 
  • Marcin Rosmus
    Marcin Rosmus
    National Synchrotron Radiation Centre SOLARIS, Jagiellonian University, Czerwone Maki 98, PL-30392 Kraków, Poland
    More by Marcin Rosmus
    Orcidhttps://orcid.org/0000-0002-4314-9601
  • , 
  • Gianluca D’Olimpio
    Gianluca D’Olimpio
    Department of Physical and Chemical Sciences, University of L’Aquila, via Vetoio, I-67100 L’Aquila (AQ), Italy
    More by Gianluca D’Olimpio
    Orcidhttps://orcid.org/0000-0002-6367-3945
  • , 
  • Marian Cosmin Istrate
    Marian Cosmin Istrate
    National Institute of Materials Physics, Atomistilor 405A, 077125 Magurele, Romania
    More by Marian Cosmin Istrate
  • , 
  • Grazia Giuseppina Politano
    Grazia Giuseppina Politano
    Department of Information Engineering, Infrastructures and Sustainable Energy (DIIES), University “Mediterranea” of Reggio Calabria, Loc. Feo di Vito, I-89122 Reggio Calabria, Italy
    More by Grazia Giuseppina Politano
  • , 
  • Ivana Vobornik
    Ivana Vobornik
    Istituto Officina dei Materiali (IOM)−CNR, Laboratorio TASC, Area Science Park, S.S.14, km 163.5, I-34149 Trieste, Italy
    More by Ivana Vobornik
    Orcidhttps://orcid.org/0000-0001-9957-3535
  • , 
  • Raman Sankar
    Raman Sankar
    Institute of Physics, Academia Sinica Nankang, Taipei 11529, Taiwan
    More by Raman Sankar
    Orcidhttps://orcid.org/0000-0003-4702-2517
  • , 
  • Corneliu Ghica
    Corneliu Ghica
    National Institute of Materials Physics, Atomistilor 405A, 077125 Magurele, Romania
    More by Corneliu Ghica
    Orcidhttps://orcid.org/0000-0001-7110-1544
  • , 
  • Junfeng Gao*
    Junfeng Gao
    Key Laboratory of Materials Modification by Laser, Ion and Electron Beams, Ministry of Education, School of Physics, Dalian University of Technology, Dalian 116024, China
    *[email protected]
    More by Junfeng Gao
    Orcidhttps://orcid.org/0000-0001-5732-9905
  • , and 
  • Antonio Politano*
    Antonio Politano
    Department of Physical and Chemical Sciences, University of L’Aquila, via Vetoio, I-67100 L’Aquila (AQ), Italy
    *[email protected]
    More by Antonio Politano
    Orcidhttps://orcid.org/0000-0002-4254-2102
Cite this: J. Phys. Chem. Lett. 2023, 14, 13, 3120–3125
Publication Date (Web):March 23, 2023
https://doi.org/10.1021/acs.jpclett.3c00005

Copyright © 2022 The Authors. Published by American Chemical Society. This publication is licensed under

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Abstract

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Nonmagnetic chiral crystals are a new class of systems hosting Kramers–Weyl Fermions, arising from the combination of structural chirality, spin–orbit coupling (SOC), and time-reversal symmetry. These materials exhibit nontrivial Fermi surfaces with SOC-induced Chern gaps over a wide energy range, leading to exotic transport and optical properties. In this study, we investigate the electronic structure and transport properties of CdAs2, a newly reported chiral material. We use synchrotron-based angle-resolved photoelectron spectroscopy (ARPES) and density functional theory (DFT) to determine the Fermiology of the (110)-terminated CdAs2 crystal. Our results, together with complementary magnetotransport measurements, suggest that CdAs2 is a promising candidate for novel topological properties protected by the structural chirality of the system. Our work sheds light on the details of the Fermi surface and topology for this chiral quantum material, providing useful information for engineering novel spintronic and optical devices based on quantized chiral charges, negative longitudinal magnetoresistance, and nontrivial Chern numbers.

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Crystal symmetries play a pivotal role in determining the electronic properties of various quantum systems, and their study has garnered substantial interest for both fundamental research and technological applications. (1−9) Crystals exhibiting well-defined handedness, due to the breaking of inversion, mirror, or any other roto-inversion symmetries, are referred to as chiral crystals. (10−12) Even in their nonmagnetic state, these chiral crystals show universal topological electronic properties due to their spin–orbit coupling and crystalline chirality, resulting in the presence of Kramers–Weyl Fermions in their spectrum. (13,14) These Fermions are pinned to Kramers degenerate points, leading to the appearance of topological gaps, which are significantly larger than those observed in Weyl semimetals. (13) Within such gaps, ubiquitous topological properties, such as quantized chiral charges, (15) negative longitudinal magnetoresistance, (16) and nontrivial Chern numbers (17) can arise, opening up exciting avenues for engineering exotic transport phenomena and applications. Furthermore, Kramers–Weyl Fermions differ from conventional Weyl Fermions as they occur at time-reversal invariant points in momentum space. SOC, structural chirality, and time-reversal symmetry combine to produce these unique properties, which can also enable additional exotic phenomena such as magneto-chiral dichroism, (18,19) large optical activity, (20,21) and even the emergence of skyrmions with the lifting of time-reversal symmetry. (22,23) As such, understanding the electronic structure of these compounds is of paramount importance, especially given the evident potential for technological applications in spintronics and optics. (11)
In this study, we investigate the electronic structure of the newly reported (24,25) chiral material CdAs2 using synchrotron-based angle-resolved photoelectron spectroscopy (ARPES), density functional theory (DFT), and transport experiments, shedding light on the details of the Fermi surface and topology for this chiral quantum material. Our findings suggest that CdAs2 is a promising candidate for enabling novel topological properties protected by its structural chirality, offering useful information for the development of disruptive spintronic and optical devices based on quantized chiral charges, negative longitudinal magnetoresistance, and nontrivial Chern numbers.
CdAs2 exhibits trigonal symmetry belonging to the space group n. 98, I4122(see Figure 1). The lattice parameters a = b = 8.152 Å and c = 4.771 Å were determined from our X-ray diffraction (XRD) measurements (Figure 2c). The crystal structure reflects the chirality of the system, with atoms forming spiral chains of covalent As–As and Cd–As bonds (Figure 1a), which influence both the optical and electronic properties.

Figure 1

Figure 1. Crystal structure and electronic band structure of bulk CdAs2. (a) Optimized primitive (left) and conventional (right) unit cells of CdAs2. (b) First Brillouin zone of the primitive cell. (c) Calculated electronic band structure without SOC effects. (d) Calculated electronic band structure including SOC effects. The Fermi level is set to zero and marked by a horizontal red dashed line. Cd and As atoms are represented by yellow and purple balls, respectively. The Kramers–Weyl nodes (d) are marked by yellow circles.

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Figure 2

Figure 2. Characterization of the CdAs2 single crystal. (a) High-resolution transmission electron microscopy (HR-TEM) image showing the crystalline structure of CdAs2. (b) Small-area electron diffraction (SAED) pattern confirming the single crystal nature of CdAs2, although the existence of elongated spots is a fingerprint of a slight mosaicity. (c) X-ray diffraction (XRD) pattern revealing the high quality of the crystal with sharp Bragg peaks. (d) Temperature-dependent magnetoresistance curve of CdAs2 single crystal showing a linear dependence at low temperatures and a saturation behavior at high temperatures.

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The electronic structure of the bulk, along the high-symmetry directions (for Brillouin zone, BZ, see Figure 1b), shows a small indirect energy gap (∼0.13 eV) as displayed in Figure 1c, indicating the semiconducting nature of the bulk crystal. The inclusion of SOC reduces the gap by approximately 20 meV, as shown in Figure 1d, but the semiconducting character is retained. With the inclusion of SOC, the band structure of CdAs2 displays a 2-fold splitting, whereas in its absence, it exhibits a 2-fold spin degeneracy. However, at time-reversal-invariant-momenta, 2-fold spin degeneracy is retained even in the presence of SOC, which is crucial for the emergence of Kramers–Weyl Fermions. (11,12)
We calculated the Wannier charge centers for six time reversal invariant planes: k1 = (0.0, 0.5), k2 = (0.0, 0.5), k3 = (0.0, 0.5) of primitive CdAs2, as shown in Figure S4 in the Supporting Information. The results indicate that the k2–k3 plane and the k1–k3 plane have a reverse topological number Z2, i.e., Z2(k1 = 0) = Z2(k2 = 0.5) = 0, Z2(k1 = 0.5) = Z2(k2 = 0.0) = 1. We hypothesized that this may be attributed to the structural chirality of CdAs2. It is worth noting that the surface electronic structure may differ significantly from the bulk. In this study, we examine four possible surface terminations along the (110) plane: As–S1, As–S2, Cd–S1, and Cd–S2 (refer to Figure S1 in the Supporting Information). Using DFT calculations, we found that the As–S1 and Cd–S1 surfaces are notably more stable than the others, without any observed distortions. Conversely, the As–S2 and Cd–S2 surfaces exhibit reconstruction, where the topmost Cd atoms in Cd–S2 sink into the As-sublayer. This behavior is comparable to a self-passivation mechanism reported in three-dimensional Dirac semimetal Cd3As2. (26)
To determine the most realistic configuration for comparison to the experiment, we relaxed the (2 × 1) and (3 × 1) supercells of As–S1, As–S2, Cd–S1, and Cd–S2 terminated (110) surface to simulate their electronic structure (Figure 3). The surface formation energy as a function of the chemical potential of As atoms (μAs) for the four types of surfaces (with a thickness of 17 Å) is illustrated in Figure S2a. The Cd–S1 termination exhibits the lowest surface energy for lower μAs (blue line in Figure S2a in the Supporting Information), following a linear trend. Conversely, the As–S1 termination yields the lowest surface energy in a richer As environment. This trend holds for various thicknesses; the surface energy appears unaffected by slab thickness (refer to Figure S2a–d in the Supporting Information for calculations from 17 to 35 Å). Therefore, we focus on the As–S1 and Cd–S1 surfaces, which exhibit the lowest and most favorable surface energy configurations, in our further analysis of (110)-oriented crystals.

Figure 3

Figure 3. Top (left panel) and side (right panel) view of (2 × 1) (top panel) and (3 × 1) (bottom panel) supercell of (a) As–S1, (b) As–S2, (c) Cd–S1, and (d) Cd–S2, respectively. Lighter colors represent lower atoms for better visualization of surface atoms.

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CdAs2 single crystals with (110) orientation were analyzed using high-resolution transmission electron microscopy (HR-TEM, Figure 2a,b). The unit cell parameters, determined to be a = b = 0.795 nm and c = 0.467 nm, were found to be consistent with previous reports (27) and XRD results (Figure 2c). Temperature-dependent magnetoresistance measurements were carried out on the same crystals, revealing a semiconductor-metal transition that is quenched with increasing magnetic field. The data in Figure 2d demonstrate that the semiconducting behavior persists below 150 K and becomes metallic above this threshold. (28) The experimental results support the conclusion that CdAs2 undergoes a transition from semiconductor to metal with increasing temperature.
The electronic structure of CdAs2 was probed using synchrotron-based ARPES. Consistent with the bulk semiconducting nature of the material, the ARPES spectra showed an energy gap separating the valence and conduction bands (Figure 4 and 5). The constant energy maps (Figure 4a–c) revealed a complex Fermiology, particularly for the valence band manifold, with small metallic conduction band pockets comprising the Fermi surface (Figure 4a). The energy-momentum dispersion along high-symmetry directions (Figure 5) indicated the presence of strongly dispersing bands with broad features, suggestive of the three-dimensional nature of the material, which introduces a significant kz contribution in ARPES measurements.

Figure 4

Figure 4. (a) Fermi surface of CdAs2 showing the electron pockets of the conduction band at the Fermi level, covering several Brillouin zones. (b) Constant energy surface at 1 eV and (c) 2.35 eV below the Fermi level illustrating the valence band structure evolution at higher k-values. The measurements were carried out at 40 K using hν = 100 eV photons in horizontal polarization setups. On the constant energy cuts, the projection of the Wigner–Seitz cells were overlaid and high-symmetry points were marked.

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Figure 5

Figure 5. Experimental band structure of bulk CdAs2 along various high-symmetry directions. (a) ARPES repeated along the X–M–X path, showing a large view of the valence band structure. (b) Second derivative plot to aid the visualization of the states. (c) Zoomed-in view of part a near the Fermi level, highlighting the pockets belonging to the conduction band manifold. (d) ARPES valence band structure measured along the Z–M–Z path (negative kx values). (e) Corresponding second derivative plot. The Z–M–Z path was also collected at positive kx values and shown in part f along with the (g) second derivative. The valence band was also measured along the (h, i) P–X–P path and (j, k) Z–P direction.

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DFT calculations predicted the presence of metallic in-gap surface states that cross the Fermi level for the most stable As-terminated surface, where the presence of dangling bonds is expected to generate these states. Band structures were calculated for As–S1 (110) and Cd–S1 (110) surfaces with thicknesses of 17–35 Å (Figure S3 in the Supporting Information), revealing that the surface states of As–S1 (110) and Cd–S1 (110) surfaces are metallic and cross the Fermi energy level (Figure S5 in the Supporting Information). The As–S1 (110) surface showed decreasing conduction bands at the Γ point as thickness increased from 17 to 35 Å, while the conduction band at Γ from the topmost As atoms of As–S1 (110) surface decreased from 0.43 to 0.34 eV. The Cd–S1 (110) surface, on the other hand, showed surface states that crossed the Fermi energy level regardless of the slab thickness, indicating that the Cd–S1 surface is more active and less stable than the As–S1 surface. To further investigate the surface state of As–S1 and Cd–S1 (110) surfaces, Wannier90 code (29) and Wannier Tools (30) package were used (Figure S4 in the Supporting Information). A tight-binding model generated by Wannier90 code confirmed that the surface state of As–S1 (110) surface slightly crosses the Fermi energy level in the direction of Γ to X, while the Cd–S1 (110) surface has several surface states crossing the Fermi energy level.
Although the identification of surface states in ARPES spectra was challenging due to their broad and intense spectral features, derivative plots of the bands (Figure 5) facilitated a more detailed comparison between theory and experiment, revealing additional dispersing features in the gap region, potentially attributed to the surface states. The comparison of theoretical band structure in Figure 1d with the experimental results in Figure 5 showed a maximum of the valence band at the M point, where Kramers–Weyl Fermions are imposed by the T symmetry.
The chirality and lack of mirror (inversion) symmetry in CdAs2 are of great significance, as they give rise to topological gaps that are much larger than those found in conventional Weyl semimetals. These gaps are clearly evident in our ARPES experiment and make CdAs2 an ideal platform for studying a range of unique phenomena. Notably, the topological properties of this material enable the existence of Kramers–Weyl Fermions, which have been suggested as promising candidates for developing novel spin-torque devices and quantum solenoids. (31)
In summary, our study has provided a comprehensive investigation of the electronic properties of CdAs2. Our results demonstrate that CdAs2 is a semiconducting chiral material with a small gap that can be overcome by thermal activation, leading to a semiconducting-metal transition. We found that the topological properties of this material are mediated by SOC, although it has a minor effect in reducing the gap size. Furthermore, we showed that the presence of metallic states on the material’s surface is crucial in enabling additional metallic states. Although identifying these surface states by ARPES is complicated due to the broadening of the spectra, our experimental results are consistent with our theoretical model.
Our findings have significant implications for the development of optical and spintronic devices based on quantized chiral charges, negative longitudinal magnetoresistance, and nontrivial Chern numbers associated with this chiral quantum material and its Kramers–Weyl Fermions.

Methods

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Theory. First-principles calculations were performed by using the Vienna ab initio simulation package (VASP). (32) The exchange-correlation interaction was described using the Perdew–Burke–Ernzerhof (PBE) functional (33) in the generalized gradient approximation (GGA), with core electrons described by the Projector-augmented wave (PAW) technology. (34) A plane-wave basis kinetic energy cutoff of 500 eV and a convergence criterion of 10–5 eV were used in the calculations. All configurations were fully relaxed until the force was lower than 0.02 eV/Å, with a k-point sampling of 0.02 1/Å used for structural relaxation.
Crystal Growth. CdAs2 single crystals were grown by the Chemical Vapor Transport (CVT) method, using Cd metal chunks (purity 99.99%), As chunks (purity 99.999%), and I2 transport agent (purity 99.999% analytical grade) purchased from Alfa Aesar Chemical in a weight ratio of 43:57. The growth process was carried out in a carbon-coated quartz tube, sealed under an Ar gas atmosphere using a glovebox. A horizontal two-zone furnace with programmable temperature and time was used to maintain the furnace hot and cold zones at 600 and 550 °C, respectively, for 2 weeks. The grown crystals were collected, washed in a glovebox to protect them from surface oxidation, and further washed with ethanol to remove any surface contamination from I2.
TEM. HR-TEM investigation of the grain surface was performed on crystal grains hanging freely in carbon membrane holes with no support underneath. We selected grains tilted to the nearest available zone axis orientation, as shown in the selected area electron diffraction (SAED) patterns in Figure 2b. HR-TEM micrographs were acquired from the thinnest regions at the grain border.
ARPES. ARPES measurements were carried out at the National Synchrotron Radiation Centre SOLARIS in Cracow, Poland, using the variable polarization and high-resolution URANOS beamline depicted in Figure S6 in the Supporting Information. Samples were glued with epoxy resin to a sample holder and cleaved in an ultrahigh vacuum by a metal post. The experiment was conducted using a quasiperiodic elliptically polarizing undulator APPLE II type as a photon source. Experimental data were collected by a VGScienta DA30L electron spectrometer, with an energy and angle resolution better than 3 meV and 0.1°, respectively. Data measurements were performed at T = 40 K and for an energy range from 20 to 140 eV. The spot size on the sample was 250 × 250 μm.
Transport Experiments. The temperature-dependent transport properties were investigated using a 4-probe measurement with the magnetic field varying from 0 to 2 T in a Quantum Design (QD) based Physical Property Measurement System (PPMS).

Supporting Information

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The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.jpclett.3c00005.

  • Further information on the theoretical model and geometry of ARPES experiments (PDF)

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Most electronic Supporting Information files are available without a subscription to ACS Web Editions. Such files may be downloaded by article for research use (if there is a public use license linked to the relevant article, that license may permit other uses). Permission may be obtained from ACS for other uses through requests via the RightsLink permission system: http://pubs.acs.org/page/copyright/permissions.html.

Author Information

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  • Corresponding Authors
  • Authors
    • Federico Mazzola - Istituto Officina dei Materiali (IOM)−CNR, Laboratorio TASC, Area Science Park, S.S.14, km 163.5, I-34149 Trieste, Italy;  Department of Molecular Sciences and Nanosystems, Ca’ Foscari University of Venice, I-30172 Venice, Italy
    • Yanxue Zhang - Key Laboratory of Materials Modification by Laser, Ion and Electron Beams, Ministry of Education, School of Physics, Dalian University of Technology, Dalian 116024, China
    • Natalia Olszowska - National Synchrotron Radiation Centre SOLARIS, Jagiellonian University, Czerwone Maki 98, PL-30392 Kraków, Poland
    • Marcin Rosmus - National Synchrotron Radiation Centre SOLARIS, Jagiellonian University, Czerwone Maki 98, PL-30392 Kraków, Poland;  Orcidhttps://orcid.org/0000-0002-4314-9601
    • Gianluca D’Olimpio - Department of Physical and Chemical Sciences, University of L’Aquila, via Vetoio, I-67100 L’Aquila (AQ), Italy;  Orcidhttps://orcid.org/0000-0002-6367-3945
    • Marian Cosmin Istrate - National Institute of Materials Physics, Atomistilor 405A, 077125 Magurele, Romania
    • Grazia Giuseppina Politano - Department of Information Engineering, Infrastructures and Sustainable Energy (DIIES), University “Mediterranea” of Reggio Calabria, Loc. Feo di Vito, I-89122 Reggio Calabria, Italy
    • Ivana Vobornik - Istituto Officina dei Materiali (IOM)−CNR, Laboratorio TASC, Area Science Park, S.S.14, km 163.5, I-34149 Trieste, Italy;  Orcidhttps://orcid.org/0000-0001-9957-3535
    • Raman Sankar - Institute of Physics, Academia Sinica Nankang, Taipei 11529, Taiwan;  Orcidhttps://orcid.org/0000-0003-4702-2517
    • Corneliu Ghica - National Institute of Materials Physics, Atomistilor 405A, 077125 Magurele, Romania;  Orcidhttps://orcid.org/0000-0001-7110-1544
  • Author Contributions

    F.M., Y.Z., N.O., and M.R. contributed equally.

  • Notes
    The authors declare no competing financial interest.

Acknowledgments

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This work was supported by the National Natural Science Foundation of China (Grant No. 12074053, 91961204, 12004064), and National Foreign Expert Project (G2022127004L). A.P. thanks CERIC-ERIC for the access to the TEM facility. M.C.I. and C.G. acknowledge funding through contract POC 332/390008/29.12.2020-SMIS 109522. R.S. acknowledges the financial support provided by the Ministry of Science and Technology in Taiwan under project numbers NSC-111-2124-M-001-009; NSC-110-2112-M-001-065-MY3; AS-iMATE-111-12.

References

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This article references 34 other publications.

  1. 1
    Kang, L.; Cao, Z. Y.; Wang, B. Pressure-Induced Electronic Topological Transition and Superconductivity in Topological Insulator Bi2Te2.1Se0.9. J. Phys. Chem. Lett. 2022, 13, 11521– 11527,  DOI: 10.1021/acs.jpclett.2c02981
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    1
    Pressure-Induced Electronic Topological Transition and Superconductivity in Topological Insulator Bi2Te2.1Se0.9
    Kang, Lei; Cao, Zi-Yu; Wang, Bo
    Journal of Physical Chemistry Letters (2022), 13 (49), 11521-11527CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
    One approach to discovering topol. superconductors is establishing supercond. based on well-identified topol. insulators. However, the coexistence of supercond. and a topol. state is always arcane. In this paper, we report how pressure tunes the crystal structure, electronic structure, and supercond. in topol. insulator Bi2Te2.1Se0.9. At ~ 2.5 GPa, the abnormal changes in c/a and the full width at half-max. of the A1g1 mode indicate the occurrence of an electronic topol. transition. The pressure-induced supercond. in Bi2Te2.1Se0.9 pinned with an electronic topol. transition presents at 2.4 GPa, which is far below the structural phase transition pressure of 8.4 GPa. These results suggest that the appearance of an electronic topol. transition is closely correlated with supercond. in the initial phase, where the topol. surface state persists. Our work clarifies the complex electronic structure of Bi2Te2.1Se0.9 and sheds light on the mechanism for supercond. in topol. insulators.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38XjtVerur3K&md5=fafe5071714e82f63cc3a7daf369a8ab
  2. 2
    Kirby, R. J.; Scholes, G. D.; Schoop, L. M. Square-Net Topological Semimetals: How Spectroscopy Furthers Understanding and Control. J. Phys. Chem. Lett. 2022, 13, 838– 850,  DOI: 10.1021/acs.jpclett.1c03798
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    2
    Square-Net Topological Semimetals: How Spectroscopy Furthers Understanding and Control
    Kirby, Robert J.; Scholes, Gregory D.; Schoop, Leslie M.
    Journal of Physical Chemistry Letters (2022), 13 (3), 838-850CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
    A review. Square-net materials are well positioned to lead optical spectroscopic explorations into the electronic structure, photoinduced dynamics, and phase transitions in topol. semimetals. Hundreds of square-net topol. semimetals can be prepd. that have remarkably different electronic and optical properties despite having similar structures. Here we present what has been gleaned recently from these materials with the whole gamut of optical spectroscopies, ranging from steady-state reflectance and Raman investigations into topol. band structures, electronic correlations, and equil. phase transitions to time-resolved techniques used to decipher ultrafast relaxation dynamics and nonequil. photoinduced phase transitions. We end with a discussion of some major remaining questions and possible future research directions.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38Xhtl2gsb4%253D&md5=c52b9845e7c24d43667928134ecc44d7
  3. 3
    Klimovskikh, I. I.; Estyunin, D. A.; Makarova, T. P.; Tereshchenko, O. E.; Kokh, K. A.; Shikin, A. M. Electronic Structure of Pb Adsorbed Surfaces of Intrinsic Magnetic Topological Insulators. J. Phys. Chem. Lett. 2022, 13, 6628– 6634,  DOI: 10.1021/acs.jpclett.2c01245
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    3
    Electronic structure of Pb adsorbed surfaces of intrinsic magnetic topological insulators
    Klimovskikh, Ilya I.; Estyunin, Dmitry A.; Makarova, Tatyana P.; Tereshchenko, Oleg E.; Kokh, Konstantin A.; Shikin, Alexander M.
    Journal of Physical Chemistry Letters (2022), 13 (29), 6628-6634CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
    Recently discovered intrinsic magnetic topol. insulators (IMTIs) constitute a unique class of quantum materials that combine magnetism and nontrivial topol. One of the most promising applications of these materials is Majorana fermion creation; Majorana fermions are expected to arise when a superconductor is in contact with the surface of an IMTI. Here we study the adsorption of Pb ultrathin films on top of IMTIs of various stoichiometries. By means of XPS we figure out the formation of the Pb wetting layer coupled to the surface atoms for low coverages and overlayer growth on top upon further deposition. Investigation of the adsorbed surfaces by means of ARPES shows the Dirac cone survival, its shift in a binding energy, and the Pb electronic states appearance. The obtained results allow the Pb/IMTI interfaces to be constructed for the understanding of the proximity effect and provide an important step toward quantum device engineering based on IMTIs.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38Xhsl2ntbnP&md5=803fd7b69bbed87ac9f4cdffeb91a329
  4. 4
    Li, L.; Gunasekaran, S.; Wei, Y.; Nuckolls, C.; Venkataraman, L. Reversed Conductance Decay of 1d Topological Insulators by Tight-Binding Analysis. J. Phys. Chem. Lett. 2022, 13, 9703– 9710,  DOI: 10.1021/acs.jpclett.2c02812
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    4
    Reversed Conductance Decay of One-Dimensional Topological Insulators by Tight-Binding Analysis
    Li, Liang; Gunasekaran, Suman; Wei, Yujing; Nuckolls, Colin; Venkataraman, Latha
    Journal of Physical Chemistry Letters (2022), 13 (41), 9703-9710CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
    Reversed conductance decay describes increasing conductance of a mol. chain series with increasing chain length. Realizing reversed conductance decay is an important step toward making long and highly conducting mol. wires. Recent work has shown that one-dimensional topol. insulators (1D TIs) can exhibit reversed conductance decay due to their nontrivial edge states. The Su-Schrieffer-Heeger (SSH) model for 1D TIs relates to the electronic structure of these isolated mols. but not their electron transport properties as single-mol. junctions. Herein, we use a tight-binding approach to demonstrate that polyacetylene and other diradicaloid 1D TIs show a reversed conductance decay at the short chain limit. We explain these conductance trends by analyzing the impact of the edge states in these 1D systems on the single-mol. junction transmission. Addnl., we discuss how the self-energy from the electrode-mol. coupling and the on-site energy of the edge sites can be tuned to create longer wires with reversed conductance decays.
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  5. 5
    Li, Y.; Zhang, Y. F.; Deng, J.; Dong, W. H.; Sun, J. T.; Pan, J.; Du, S. Rational Design of Heteroanionic Two-Dimensional Materials with Emerging Topological, Magnetic, and Dielectric Properties. J. Phys. Chem. Lett. 2022, 13, 3594– 3601,  DOI: 10.1021/acs.jpclett.2c00620
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    5
    Rational Design of Heteroanionic Two-Dimensional Materials with Emerging Topological, Magnetic, and Dielectric Properties
    Li, Yuhui; Zhang, Yan-Fang; Deng, Jun; Dong, Wen-Han; Sun, Jia-Tao; Pan, Jinbo; Du, Shixuan
    Journal of Physical Chemistry Letters (2022), 13 (16), 3594-3601CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
    Designing and tuning the phys. properties of two-dimensional (2D) materials at the at. level are crucial to the development of 2D technologies. Here, we introduce heteroanions into metal-centered octahedral structural units of a 2D crystal breaking the Oh symmetry, together with the synergistic effect of anions' electrons and electronegativity, to realize ternary 2D materials with emerging topol., magnetic, and dielec. properties. Using an intrinsic heteroanionic van der Waals layered material, VOCl, as a prototype, 20 2D monolayers VXY (X = B, C, N, O, or F; Y = F, Cl, Br, or I) are obtained and investigated by means of first-principles calcns. The anion engineering in this family significantly reshapes the electronic properties of VOCl, leading to nonmagnetic topol. insulators with nontrivial edge states in VCY, ferromagnetic half-semimetals with a nodal ring around the Fermi energy in VNY, and insulators with dielec. consts. in VOY higher than that of h-BN. This work demonstrates the rationality and validity of the design strategy of multiple-anion engineering to achieve superior properties in the 2D monolayers with potential application in electronics and spintronics.
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  6. 6
    Liang, Y.; Zheng, F.; Zhao, P.; Wang, Q.; Frauenheim, T. Intrinsic Ferroelectric Quantum Spin Hall Insulator in Monolayer Na3Bi with Surface Trimerization. J. Phys. Chem. Lett. 2022, 13, 11059– 11064,  DOI: 10.1021/acs.jpclett.2c03270
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    6
    Intrinsic ferroelectric quantum spin Hall insulator in monolayer Na3Bi with surface trimerization
    Liang, Yan; Zheng, Fulu; Zhao, Pei; Wang, Qiang; Frauenheim, Thomas
    Journal of Physical Chemistry Letters (2022), 13 (48), 11059-11064CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
    Two-dimensional (2D) ferroelec. quantum spin Hall (FEQSH) insulator, which features coexisting ferroelec. and topol. insulating orders in two-dimension, is generally considered available only in engineered 2D systems. This is detrimental to the synthesis and application of next generation nonvolatile functional candidates. Therefore, exploring the intrinsic 2D FEQSH insulator is crucial. Here, by means of first-principles, we report a long-thought intrinsic 2D FEQSH insulator in monolayer Na3Bi with surface trimerization. The material harbors merits including large ferroelec. polarization, sizable nontrivial band gap, and low switching barrier, which are particularly beneficial for the detection and observation of ferroelec. topol. insulating states. Also, it is capable of nonvolatile switching of nontrivial spin textures via inherent ferroelectricity. The fantastic combination of excellent ferroelec. and topol. phases in intrinsic the Na3Bi monolayer serves as an alluring platform for accelerating both scientific discoveries and innovative applications.
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  7. 7
    Xi, M.; Chen, F.; Gong, C.; Tian, S.; Yin, Q.; Qian, T.; Lei, H. Relationship between Antisite Defects, Magnetism, and Band Topology in MnSb2Te4 Crystals with Tc≈ 40 K. J. Phys. Chem. Lett. 2022, 13, 10897– 10904,  DOI: 10.1021/acs.jpclett.2c02775
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    7
    Relationship between Antisite Defects, Magnetism, and Band Topology in MnSb2Te4 Crystals with TC ≈ 40 K
    Xi, Ming; Chen, Famin; Gong, Chunsheng; Tian, Shangjie; Yin, Qiangwei; Qian, Tian; Lei, Hechang
    Journal of Physical Chemistry Letters (2022), 13 (47), 10897-10904CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
    MnSb2Te4 has attracted extensive attention because of its rich and adjustable magnetic properties. Here, using a modified crystal growth method, ferrimagnetic MnSb2Te4 crystals with enhanced Curie temp. (TC) of about 40 K with dominant hole-type carriers and intrinsic anomalous Hall effect is obtained. Time- and angle-resolved photoemission spectroscopy reveals that surface states are absent in both antiferromagnetic and ferrimagnetic MnSb2Te4, implying that they have topol. trivial electronic structures. We propose that the enhancement of ferrimagnetism mainly originates from the increase of intralayer magnetic coupling caused by the decrease of Sb content at Mn sites when the decrease of Mn concn. at Sb sites would prefer the nontrival band topol. Moreover, it is known that the initial satn. moment (Mis) is sensitive to the concns. of Mn/Sb antisite defects; thus, the Mis could be a valuable parameter to evaluate the magnetic and topol. properties of MnX2nTe3n+1 (X = Bi, Sb) families.
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  8. 8
    Yakovlev, D. S.; Lvov, D. S.; Emelyanova, O. V.; Dzhumaev, P. S.; Shchetinin, I. V.; Skryabina, O. V.; Egorov, S. V.; Ryazanov, V. V.; Golubov, A. A.; Roditchev, D.; Stolyarov, V. S. Physical Vapor Deposition Features of Ultrathin Nanocrystals of Bi2(TexSe1-X)3. J. Phys. Chem. Lett. 2022, 13, 9221– 9231,  DOI: 10.1021/acs.jpclett.2c02664
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    8
    Physical Vapor Deposition Features of Ultrathin Nanocrystals of Bi2(TexSe1-x)3
    Yakovlev, Dmitry S.; Lvov, Dmitry S.; Emelyanova, Olga V.; Dzhumaev, Pave S.; Shchetinin, Igor V.; Skryabina, Olga V.; Egorov, Sergey V.; Ryazanov, Valery V.; Golubov, Alexander A.; Roditchev, Dimitri; Stolyarov, Vasily S.
    Journal of Physical Chemistry Letters (2022), 13 (39), 9221-9231CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
    Structural and electronic properties of ultrathin nanocrystals of chalcogenide Bi2(Tex Se1-x)3 were studied. The nanocrystals were formed from the parent compd. Bi2Te2Se on as-grown and thermally oxidized Si(100) substrates using Ar-assisted phys. vapor deposition, resulting in well-faceted single crystals several quintuple layers thick and a few hundreds nanometers large. The chem. compn. and structure of the nanocrystals were analyzed by energy-dispersive X-ray spectroscopy, XPS, electron backscattering, and X-ray diffraction. The electron transport through nanocrystals connected to superconducting Nb electrodes demonstrated Josephson behavior, with the predominance of the topol. channels []. The present paper focuses on the effect of the growth conditions on the morphol., structural, and electronic properties of nanocrystals.
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  9. 9
    (a) Zhou, Z.; Peng, K.; Xiao, S.; Wei, Y.; Dai, Q.; Lu, X.; Wang, G.; Zhou, X. Anomalous Thermoelectric Performance in Asymmetric Dirac Semimetal BaAgBi. J. Phys. Chem. Lett. 2022, 13, 2291– 2298,  DOI: 10.1021/acs.jpclett.2c00379
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    9a
    Anomalous Thermoelectric Performance in Asymmetric Dirac Semimetal BaAgBi
    Zhou, Zizhen; Peng, Kunling; Xiao, Shijuan; Wei, Yiqing; Dai, Qinjin; Lu, Xu; Wang, Guoyu; Zhou, Xiaoyuan
    Journal of Physical Chemistry Letters (2022), 13 (10), 2291-2298CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
    Multiple-band degeneracy has been widely recognized to be beneficial for high thermoelec. performance. Here, we discover that the p-type Dirac bands with lower degeneracy synergistically produce a higher Seebeck coeff. and elec. cond. in topol. semimetal BaAgBi. The anomalous transport phenomenon intrinsically originated from the asym. electronic structures: (i) complete p-type Dirac bands near the Fermi level facilitate high and strong energy-dependent hole relaxation time; (ii) the presence of addnl. parabolic conduction valleys allows for a large d. of states to accept scattered electrons, leading to an enlarged hole-electron relaxation time ratio and, thus, weakened bipolar effect. In combination with the strong lattice anharmonicity, an exceptional p-type av. ZT of 0.42 is achieved from 300 to 600 K, which can be dramatically enhanced to 1.38 via breaking the C3v symmetry. This work uncovers the underlying mechanisms governing the abnormal transport behavior in Dirac semimetal BaAgBi and highlights the asym. electronic structures as target features to discover/design high-performance thermoelec. materials.
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    .
    (b) Borca, B.; Michnowicz, T.; Aguilar-Galindo, F.; Pétuya, R.; Pristl, M.; Schendel, V.; Pentegov, I.; Kraft, U.; Klauk, H.; Wahl, P. Chiral and Catalytic Effects of Site-Specific Molecular Adsorption. J. Phys. Chem. Lett. 2023, 14 (8), 2072– 2077,  DOI: 10.1021/acs.jpclett.2c03575
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    9b
    Chiral and Catalytic Effects of Site-Specific Molecular Adsorption
    Borca, Bogdana; Michnowicz, Tomasz; Aguilar-Galindo, Fernando; Petuya, Remi; Pristl, Marcel; Schendel, Verena; Pentegov, Ivan; Kraft, Ulrike; Klauk, Hagen; Wahl, Peter; Arnau, Andres; Schlickum, Uta
    Journal of Physical Chemistry Letters (2023), 14 (8), 2072-2077CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
    The changes of properties and preferential interactions based on subtle energetic differences are important characteristics of org. mols., particularly for their functionalities in biol. systems. Only slightly energetically favored interactions are important for the mol. adsorption and bonding to surfaces, which define their properties for further technol. applications. Here, prochiral tetracenothiophene mols. are adsorbed on the Cu(111) surface. The chiral adsorption configurations are detd. by Scanning Tunneling Microscopy studies and confirmed by 1st-principles calcns. Remarkably, the selection of the adsorption sites by chem. different moieties of the mols. is dictated by the arrangement of the atoms in the 1st and 2nd surface layers. Also, the authors have studied the thermal effects on the direct desulfurization reaction that occurs under the catalytic activity of the Cu substrate. This reaction leads to a product that is covalently bound to the surface in chiral configurations.
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  10. 10
    Sanchez, D. S.; Belopolski, I.; Cochran, T. A.; Xu, X.; Yin, J.-X.; Chang, G.; Xie, W.; Manna, K.; Süß, V.; Huang, C.-Y. Topological Chiral Crystals with Helicoid-Arc Quantum States. Nature 2019, 567, 500– 505,  DOI: 10.1038/s41586-019-1037-2
    [Crossref], [PubMed], [CAS], Google Scholar
    10
    Topological chiral crystals with helicoid-arc quantum states
    Sanchez, Daniel S.; Belopolski, Ilya; Cochran, Tyler A.; Xu, Xitong; Yin, Jia-Xin; Chang, Guoqing; Xie, Weiwei; Manna, Kaustuv; Suss, Vicky; Huang, Cheng-Yi; Alidoust, Nasser; Multer, Daniel; Zhang, Songtian S.; Shumiya, Nana; Wang, Xirui; Wang, Guang-Qiang; Chang, Tay-Rong; Felser, Claudia; Xu, Su-Yang; Jia, Shuang; Lin, Hsin; Hasan, M. Zahid
    Nature (London, United Kingdom) (2019), 567 (7749), 500-505CODEN: NATUAS; ISSN:0028-0836. (Nature Research)
    The quantum behavior of electrons in materials is the foundation of modern electronics and information technol., and quantum materials with topol. electronic and optical properties are essential for realizing quantized electronic responses that can be used for next generation technol. Here, the authors report the first observation of topol. quantum properties of chiral crystals in the RhSi family. The authors find that this material class hosts a quantum phase of matter that exhibits nearly ideal topol. surface properties originating from the crystals' structural chirality. Electrons on the surface of these crystals show a highly unusual helicoid fermionic structure that spirals around two high-symmetry momenta, indicating electronic topol. chirality. The existence of bulk multiply degenerate band fermions is guaranteed by the crystal symmetries; however, to det. the topol. invariant or charge in these chiral crystals, it is essential to identify and study the helicoid topol. of the arc states. The helicoid arcs that the authors observe on the surface characterize the topol. charges of ±2, which arise from bulk higher-spin chiral fermions. These topol. conductors exhibit giant Fermi arcs of max. length (π), which are orders of magnitude larger than those found in known chiral Weyl fermion semimetals. The results demonstrate an electronic topol. state of matter on structurally chiral crystals featuring helicoid-arc quantum states. Such exotic multifold chiral fermion semimetal states could be used to detect a quantized photogalvanic optical response, the chiral magnetic effect and other optoelectronic phenomena predicted for this class of materials.
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  11. 11
    Chang, G.; Wieder, B. J.; Schindler, F.; Sanchez, D. S.; Belopolski, I.; Huang, S.-M.; Singh, B.; Wu, D.; Chang, T.-R.; Neupert, T.; Xu, S.-Y.; Lin, H.; Hasan, M. Z. Topological Quantum Properties of Chiral Crystals. Nat. Mater. 2018, 17, 978– 985,  DOI: 10.1038/s41563-018-0169-3
    [Crossref], [PubMed], [CAS], Google Scholar
    11
    Topological quantum properties of chiral crystals
    Chang, Guoqing; Wieder, Benjamin J.; Schindler, Frank; Sanchez, Daniel S.; Belopolski, Ilya; Huang, Shin-Ming; Singh, Bahadur; Wu, Di; Chang, Tay-Rong; Neupert, Titus; Xu, Su-Yang; Lin, Hsin; Hasan, M. Zahid
    Nature Materials (2018), 17 (11), 978-985CODEN: NMAACR; ISSN:1476-1122. (Nature Research)
    Chiral crystals are materials with a lattice structure that has a well-defined handedness due to the lack of inversion, mirror or other roto-inversion symmetries. Although it has been shown that the presence of cryst. symmetries can protect topol. band crossings, the topol. electronic properties of chiral crystals remain largely uncharacterized. Here we show that Kramers-Weyl fermions are a universal topol. electronic property of all non-magnetic chiral crystals with spin-orbit coupling and are guaranteed by structural chirality, lattice translation and time-reversal symmetry. Unlike conventional Weyl fermions, they appear at time-reversal-invariant momenta. We identify representative chiral materials in 33 of the 65 chiral space groups in which Kramers-Weyl fermions are relevant to the low-energy physics. We det. that all point-like nodal degeneracies in non-magnetic chiral crystals with relevant spin-orbit coupling carry non-trivial Chern nos. Kramers-Weyl materials can exhibit a monopole-like electron spin texture and topol. non-trivial bulk Fermi surfaces over an unusually large energy window.
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  12. 12
    Hasan, M. Z.; Chang, G.; Belopolski, I.; Bian, G.; Xu, S.-Y.; Yin, J.-X. Weyl, Dirac and High-Fold Chiral Fermions in Topological Quantum Matter. Nat. Rev. Mater. 2021, 6, 784– 803,  DOI: 10.1038/s41578-021-00301-3
    [Crossref], [CAS], Google Scholar
    12
    Weyl, Dirac and high-fold chiral fermions in topological quantum matter
    Hasan, M. Zahid; Chang, Guoqing; Belopolski, Ilya; Bian, Guang; Xu, Su-Yang; Yin, Jia-Xin
    Nature Reviews Materials (2021), 6 (9), 784-803CODEN: NRMADL; ISSN:2058-8437. (Nature Portfolio)
    A review Quantum materials hosting Weyl fermions have opened a new era of research in condensed matter physics. First proposed in 1929 in the context of particle physics, Weyl fermions have yet to be obsd. as elementary particles. In 2015, Weyl fermions were detected as collective electronic excitations in the strong spin-orbit coupled material tantalum arsenide, TaAs. This discovery was followed by a flurry of exptl. and theor. explorations of Weyl phenomena in materials. Weyl materials naturally lend themselves to the exploration of the topol. index assocd. with Weyl fermions and their divergent Berry curvature field, as well as the topol. bulk-boundary correspondence, giving rise to protected conducting surface states. Here, we review the broader class of Weyl topol. phenomena in materials, starting with the observation of emergent Weyl fermions in the bulk and Fermi arc states on the surface of the TaAs family of crystals by photoemission spectroscopy. We then discuss several exotic optical and magnetic responses obsd. in these materials, as well as progress in developing related chiral materials. We discuss the conceptual development of high-fold chiral fermions, which generalize Weyl fermions, and we review the observation of high-fold chiral fermion phases by taking the rhodium silicide, RhSi, family of crystals as a prime example. Lastly, we discuss recent advances in Weyl line phases in magnetic topol. materials. With this Review, we aim to provide an introduction to the basic concepts underlying Weyl physics in condensed matter, and to representative materials and their electronic structures and topol. as revealed by spectroscopic studies. We hope this work serves as a guide for future theor. and exptl. explorations of chiral fermions and related topol. quantum systems with potentially enhanced functionalities.
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  13. 13
    Tan, W.; Jiang, X.; Li, Y.; Wu, X.; Wang, J.; Huang, B. A Unified Understanding of Diverse Spin Textures of Kramers–Weyl Fermions in Nonmagnetic Chiral Crystals. Adv. Funct. Mater. 2022, 32, 2208023,  DOI: 10.1002/adfm.202208023
    [Crossref], [CAS], Google Scholar
    13
    A Unified Understanding of Diverse Spin Textures of Kramers-Weyl Fermions in Nonmagnetic Chiral Crystals
    Tan, Wei; Jiang, Xiao; Li, Yang; Wu, Xiaoqiang; Wang, Jianfeng; Huang, Bing
    Advanced Functional Materials (2022), 32 (49), 2208023CODEN: AFMDC6; ISSN:1616-301X. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Chiral crystals, characterized by rotation, screw rotation, and translation symmetries are abundant in nature. The existence of Kramers-Weyl fermions (KWFs) at the time-reversal-invariant momenta in nonmagnetic chiral crystals (NCCs) has attracted intense attention due to their unique phys. properties beyond conventional Weyl fermions. Although the spin texture, one of the most fundamental phys. quantities, is found to be dramatically different for different KWFs in different NCCs, a unified understanding of this puzzling phenomenon is still lacking. In this article, combining k · p theory and first-principles calcns., k-linear Hamiltonians for KWFs are constructed and consequently a complete classification for the spin textures of KWFs in all the NCCs is made, which are confirmed by a series of material example calcns. Interestingly, it is found that the spin textures are reversed in NCCs with opposite chirality, leading to reversed Fermi arc surface states. Importantly, this study unveils that the nonlinear optical responses around the KWFs in NCCs can be largely detd. by their spin texture classification. This study not only provides a unified understanding of the spin textures of KWFs in all the NCCs, but also suggests a principle to design novel KWF-related spintronics and nonlinear optics.
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  14. 14
    Shekhar, C. Chirality Meets Topology. Nat. Mater. 2018, 17, 953– 954,  DOI: 10.1038/s41563-018-0210-6
    [Crossref], [PubMed], [CAS], Google Scholar
    14
    Chirality meets topology
    Shekhar, Chandra
    Nature Materials (2018), 17 (11), 953-954CODEN: NMAACR; ISSN:1476-1122. (Nature Research)
    By considering the topol. of chiral crystals, a new type of massless fermion, connected with giant arc-like surface states, are predicted. Such Kramers-Weyl fermions should manifest themselves in a wide variety of chiral materials.
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  15. 15
    Chang, G.; Xu, S.-Y.; Wieder, B. J.; Sanchez, D. S.; Huang, S.-M.; Belopolski, I.; Chang, T.-R.; Zhang, S.; Bansil, A.; Lin, H. Unconventional Chiral Fermions and Large Topological Fermi Arcs in RhSi. Phys. Rev. Lett. 2017, 119, 206401,  DOI: 10.1103/PhysRevLett.119.206401
    [Crossref], [PubMed], [CAS], Google Scholar
    15
    Unconventional chiral fermions and large topological Fermi arcs in RhSi
    Chang, Guoqing; Xu, Su-Yang; Wieder, Benjamin J.; Sanchez, Daniel S.; Huang, Shin-Ming; Belopolski, Ilya; Chang, Tay-Rong; Zhang, Songtian; Bansil, Arun; Lin, Hsin; Hasan, M. Zahid
    Physical Review Letters (2017), 119 (20), 206401/1-206401/6CODEN: PRLTAO; ISSN:1079-7114. (American Physical Society)
    A review. The theor. proposal of chiral fermions in topol. semimetals has led to a significant effort towards their exptl. realization. In particular, the Fermi surfaces of chiral semimetals carry quantized Chern nos., making them an attractive platform for the observation of exotic transport and optical phenomena. While the simplest example of a chiral fermion in condensed matter is a conventional |C| = 1 Weyl fermion, recent theor. works have proposed a no. of unconventional chiral fermions beyond the std. model which are protected by unique combinations of topol. and cryst. symmetries. However, materials candidates for exptl. probing the transport and response signatures of these unconventional fermions have thus far remained elusive. In this Letter, we propose the RhSi family in space group No. 198 as the ideal platform for the exptl. examn. of unconventional chiral fermions. We find that RhSi is a filling-enforced semimetal that features near its Fermi surface a chiral double sixfold-degenerate spin-1 Weyl node at R and a previously uncharacterized fourfold-degenerate chiral fermion at Γ. Each unconventional fermion displays Chern no. ±4 at the Fermi level. We also show that RhSi displays the largest possible momentum sepn. of compensative chiral fermions, the largest proposed topol. nontrivial energy window, and the longest possible Fermi arcs on its surface. We conclude by proposing signatures of an exotic bulk photogalvanic response in RhSi.
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  16. 16
    Arnold, F.; Shekhar, C.; Wu, S.-C.; Sun, Y.; Dos Reis, R. D.; Kumar, N.; Naumann, M.; Ajeesh, M. O.; Schmidt, M.; Grushin, A. G. Negative Magnetoresistance without Well-Defined Chirality in the Weyl Semimetal TaP. Nat. Commun. 2016, 7, 1– 7,  DOI: 10.1038/ncomms11615
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  17. 17
    Tang, P.; Zhou, Q.; Zhang, S.-C. Multiple Types of Topological Fermions in Transition Metal Silicides. Phys. Rev. Lett. 2017, 119, 206402,  DOI: 10.1103/PhysRevLett.119.206402
    [Crossref], [PubMed], [CAS], Google Scholar
    17
    Multiple types of topological fermions in transition metal silicides
    Tang, Peizhe; Zhou, Quan; Zhang, Shou-Cheng
    Physical Review Letters (2017), 119 (20), 206402/1-206402/6CODEN: PRLTAO; ISSN:1079-7114. (American Physical Society)
    A review. Exotic massless fermionic excitations with nonzero Berry flux, other than the Dirac and Weyl fermions, could exist in condensed matter systems under the protection of cryst. symmetries, such as spin-1 excitations with threefold degeneracy and spin-3/2 Rarita-Schwinger-Weyl fermions. Herein, by using the ab initio d. functional theory, we show that these unconventional quasiparticles coexist with type-I and type-II Weyl fermions in a family of transition metal silicides, including CoSi, RhSi, RhGe, and CoGe, when spin-orbit coupling is considered. Their nontrivial topol. results in a series of extensive Fermi arcs connecting projections of these bulk excitations on the side surface, which is confirmed by (001) surface electronic spectra of CoSi. In addn., these stable arc states exist within a wide energy window around the Fermi level, which makes them readily accessible in angle-resolved photoemission spectroscopy measurements.
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  18. 18
    Rikken, G.; Raupach, E. Observation of Magneto-Chiral Dichroism. Nature 1997, 390, 493– 494,  DOI: 10.1038/37323
    [Crossref], [CAS], Google Scholar
    18
    Observation of magneto-chiral dichroism
    Rikken, G. L. J. A.; Raupach, E.
    Nature (London) (1997), 390 (6659), 493-494CODEN: NATUAS; ISSN:0028-0836. (Macmillan Magazines)
    Magneto-chiral dichroism was obsd. and its enantioselectivity demonstrated in Eu[(±)tfd]3 (H(±)tfd = 3-trifluoroacetyl-(±)-camphor) in DMSO-d6.
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  19. 19
    Train, C.; Gheorghe, R.; Krstic, V.; Chamoreau, L.-M.; Ovanesyan, N. S.; Rikken, G. L.; Gruselle, M.; Verdaguer, M. Strong Magneto-Chiral Dichroism in Enantiopure Chiral Ferromagnets. Nat. Mater. 2008, 7, 729– 734,  DOI: 10.1038/nmat2256
    [Crossref], [PubMed], [CAS], Google Scholar
    19
    Strong magneto-chiral dichroism in enantiopure chiral ferromagnets
    Train, Cyrille; Gheorghe, Ruxandra; Krstic, Vojislav; Chamoreau, Lise-Marie; Ovanesyan, Nikolai S.; Rikken, Geert L. J. A.; Gruselle, Michel; Verdaguer, Michel
    Nature Materials (2008), 7 (9), 729-734CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)
    As materials science is moving towards the synthesis, the study and the processing of new materials exhibiting well-defined and complex functions, the synthesis of new multifunctional materials is one of the important challenges. One of these complex phys. properties is magneto-chiral dichroism which arises, at second order, from the coexistence of spatial asymmetry and magnetization in a material. Herein the authors report the first measurement of strong magneto-chiral dichroism in an enantiopure chiral ferromagnet. The ab initio synthesis of the enantiopure chiral ferromagnet is based on an enantioselective self-assembly, where a resolved chiral quaternary ammonium cation imposes the abs. configurations of the metal centers within Cr-Mn two-dimensional oxalate layers. The ferromagnetic interaction between Cr(III) and Mn(II) ions leads to a Curie temp. of 7 K. The magneto-chiral dichroic effect is enhanced by a factor of 17 when entering into the ferromagnetic phase. Magneto-chiral dichroism is an effect in which unpolarized light is absorbed differently for parallel and antiparallel propagation with respect to an applied magnetic field. Previous observations have only seen a rather weak demonstration of this effect. Following a challenging synthesis, strong magneto-dichroism has now been obsd. in enantiopure chiral ferromagnets. Magneto-chiral dichroism is an effect in which unpolarized light is absorbed differently for parallel and antiparallel propagation with respect to an applied magnetic field. Previous observations have only seen a rather weak demonstration of this effect. Following a challenging synthesis, strong magneto-dichroism has now been obsd. in enantiopure chiral ferromagnets.
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  20. 20
    Hannam, K.; Powell, D. A.; Shadrivov, I. V.; Kivshar, Y. S. Broadband Chiral Metamaterials with Large Optical Activity. Phys. Rev. B 2014, 89, 125105,  DOI: 10.1103/PhysRevB.89.125105
    [Crossref], [CAS], Google Scholar
    20
    Broadband chiral metamaterials with large optical activity
    Hannam, Kirsty; Powell, David A.; Shadrivov, Ilya V.; Kivshar, Yuri S.
    Physical Review B: Condensed Matter and Materials Physics (2014), 89 (12), 125105/1-125105/6CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)
    We study theor. and exptl. a type of metamaterial with hybrid elements composed of twisted pairs of cross-shaped meta-atoms and their complements. We reveal that such two-layer metasurfaces demonstrate large, dispersionless optical activity at the transmission resonance accompanied by very low ellipticity. We develop a retrieval procedure to det. the effective material parameters for this structure, which has symmetry (C4) of a lower order than other commonly studied chiral structures. We verify our theor. approach by reproducing numerical and exptl. scattering parameters.
    >> More from SciFinder ®
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  21. 21
    Zhao, R.; Zhang, L.; Zhou, J.; Koschny, T.; Soukoulis, C. Conjugated Gammadion Chiral Metamaterial with Uniaxial Optical Activity and Negative Refractive Index. Phys. Rev. B 2011, 83, 035105,  DOI: 10.1103/PhysRevB.83.035105
    [Crossref], [CAS], Google Scholar
    21
    Conjugated gammadion chiral metamaterial with uniaxial optical activity and negative refractive index
    Zhao, R.; Zhang, L.; Zhou, J.; Koschny, Th.; Soukoulis, C. M.
    Physical Review B: Condensed Matter and Materials Physics (2011), 83 (3), 035105/1-035105/4CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)
    A conjugated gammadion chiral metamaterial that uniaxially exhibits huge optical activity and CD, and gives a neg. refractive index is demonstrated numerically and exptl. This chiral design provides smaller unit cell size and larger chirality compared with other published planar designs. Expts. are performed at GHz frequencies (around 6 GHz) and are in agreement with the numerical simulations.
    >> More from SciFinder ®
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  22. 22
    Tokunaga, Y.; Yu, X.; White, J.; Rønnow, H. M.; Morikawa, D.; Taguchi, Y.; Tokura, Y. A New Class of Chiral Materials Hosting Magnetic Skyrmions Beyond Room Temperature. Nat. Commun. 2015, 6, 1– 7,  DOI: 10.1038/ncomms8638
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  23. 23
    Jena, J.; Göbel, B.; Ma, T.; Kumar, V.; Saha, R.; Mertig, I.; Felser, C.; Parkin, S. S. Elliptical Bloch Skyrmion Chiral Twins in an Antiskyrmion System. Nat. Commun. 2020, 11, 1– 9,  DOI: 10.1038/s41467-020-14925-6
    [Crossref], [PubMed], Google Scholar
    There is no corresponding record for this reference.
  24. 24
    Żdanowicz, E.; Wojciechowski, W.; Misiewicz, J.; Lisunov, K. Negative Magnetoresistance for Different Orientations of N-Type Cdas2 in the Variable-Range Hopping Regime. Mater. Sci. Eng., B 1994, 26, 19– 24,  DOI: 10.1016/0921-5107(94)90181-3
    [Crossref], [CAS], Google Scholar
    24
    Negative magnetoresistance for different orientations of n-type CdAs2 in the variable-range hopping regime
    Zdanowicz, E.; Wojciechowski, W.; Misiewicz, J.; Lisunov, K. G.
    Materials Science & Engineering, B: Solid-State Materials for Advanced Technology (1994), 26 (1), 19-24CODEN: MSBTEK; ISSN:0921-5107.
    The neg. magnetoresistance of Cd diarsenide in the variable-range hopping regime near the metal-nonmetal transition was analyzed by fitting the theor. model of Altshuler to the exptl. data. Expts. were performed for two different CdAs2 crystallog. orientations: [110] and [001]. There exists a region of magnetic fields and temps. in which the behavior of the neg. magnetoresistance corresponds completely to that predicted by Altshuler.
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  25. 25
    Oubraham, A.; Biskupski, G.; Zdanowicz, E. Negative Magnetoresistance of N-Type Compensated Cadmium Arsenide (CdSs2) in the Temperature Range 11 K-4.2 K. Solid State Commun. 1991, 77, 351– 354,  DOI: 10.1016/0038-1098(91)90749-L
    [Crossref], [CAS], Google Scholar
    25
    Negative magnetoresistance of n-type compensated cadmium diarsenide in the temperature range 11 K - 4.2 K
    Oubraham, A. A.; Biskupski, G.; Zdanowicz, E.
    Solid State Communications (1991), 77 (5), 351-4CODEN: SSCOA4; ISSN:0038-1098.
    The neg. magnetoresistance in compensated n-type CdAs2 with carrier d. n = 1.7 × 1017 cm-3 has been measured in the temp. range 4.2-11 K, in magnetic fields up to 1.5 T. Longitudinal and transverse magnetoresistance have similar behaviors. The exptl. data have been analyzed according to the V. Toyozawa (1962) model which suggests an addnl. scattering process of the carriers by localized magnetic moments. The transverse magnetoresistance which is treated here has the behavior of a system of paramagnetic spins. The variation of the neg. magnetoresistance vs. magnetic field and temp. is quite well approximated by a Langevin function with an effective magnetic moment μ* = n μB where μB is the μB and n = 8.
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  26. 26
    Gao, J.; Cupolillo, A.; Nappini, S.; Bondino, F.; Edla, R.; Fabio, V.; Sankar, R.; Zhang, Y. W.; Chiarello, G.; Politano, A. Surface Reconstruction, Oxidation Mechanism, and Stability of Cd3as2. Adv. Funct. Mater. 2019, 29, 1900965,  DOI: 10.1002/adfm.201900965
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  27. 27
    Červinka, L.; Hrubý, A. The Crystal Structure of CdSs2. Acta Crystallogr. B 1970, 26, 457– 458,  DOI: 10.1107/S0567740870002650
    [Crossref], [CAS], Google Scholar
    27
    Crystal structure of CdAs2
    Cervinka, Ladislav; Hruby, A.
    Acta Crystallographica, Section B: Structural Crystallography and Crystal Chemistry (1970), 26 (Pt. 4), 457-8CODEN: ACBCAR; ISSN:0567-7408.
    CdAs2 has a tetragonal structure with a = 7.96, c = 4.67 Å, c/a = 0.59; the measured d. is 5.8 and Z = 4. The space group is D104-I4122. Four Cd atoms are in the 4(b) position and 8 As atoms in the 8(f) position, with x = 0.06 ± 0.01.
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  28. 28
    Sales, B.; Jones, E.; Chakoumakos, B.; Fernandez-Baca, J.; Harmon, H.; Sharp, J.; Volckmann, E. Magnetic, Transport, and Structural Properties of Fe1–XIrxSi. Phys. Rev. B 1994, 50, 8207,  DOI: 10.1103/PhysRevB.50.8207
    [Crossref], [CAS], Google Scholar
    28
    Magnetic, transport, and structural properties of Fe1-xIrxSi
    Sales, B. C.; Jones, E. C.; Chakoumakos, B. C.; Fernandez-Baca, J. A.; Harmon, H. E.; Sharp, J. W.
    Physical Review B: Condensed Matter and Materials Physics (1994), 50 (12), 8207-13CODEN: PRBMDO; ISSN:0163-1829.
    Magnetic susceptibility, resistivity, Seebeck, Hall, and powder x-ray and neutron-diffraction measurements were used to characterize single crystals of FeSi and polycryst. samples of Fe1-xIrxSi for x <0.2. The Rietveld refinement of low-temp. powder neutron-diffraction data on FeSi showed no change in the space group and no structural anomalies from 4 to 300 k. Magnetic and transport data from 4 to 700 K are consistent with the characterization of FeSi as a narrow-gap semiconductor (Eg = 1200 K) with strong intrasite correlations for the states just below and above the gap. Fits to the magnetic susceptibility and resistivity data suggest that the magnetic (or direct) gap may be larger than the transport (indirect) gap. Electron mobilities in FeSi are very low (3-5 cm2/V s). The thermopower of FeSi has a large pos. peak (500 μV/K) at 50 K that is attributed to an unusually strong phonon-drag mechanism. Iridium acts as an electron donor in the Fe1-xIrxSi alloys. As the iridium doping level is increased, there is a rapid decrease in the low-temp. resistivity and a large neg. (-140 μV/K) phonon-drag contribution to the thermopower. For Peltier cooling applications, a max. value for ZT of 0.07 was found for a Fe0.95Ir0.05Si alloy at 100 K.
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  29. 29
    Pizzi, G.; Vitale, V.; Arita, R.; Blugel, S.; Freimuth, F.; Geranton, G.; Gibertini, M.; Gresch, D.; Johnson, C.; Koretsune, T.; Ibanez-Azpiroz, J.; Lee, H.; Lihm, J. M.; Marchand, D.; Marrazzo, A.; Mokrousov, Y.; Mustafa, J. I.; Nohara, Y.; Nomura, Y.; Paulatto, L.; Ponce, S.; Ponweiser, T.; Qiao, J.; Thole, F.; Tsirkin, S. S.; Wierzbowska, M.; Marzari, N.; Vanderbilt, D.; Souza, I.; Mostofi, A. A.; Yates, J. R. Wannier90 as a Community Code: New Features and Applications. J. Phys.: Condens. Matter 2020, 32, 165902,  DOI: 10.1088/1361-648X/ab51ff
    [Crossref], [PubMed], [CAS], Google Scholar
    29
    Wannier90 as a community code: new features and applications
    Pizzi, Giovanni; Vitale, Valerio; Arita, Ryotaro; Blugel, Stefan; Freimuth, Frank; Geranton, Guillaume; Gibertini, Marco; Gresch, Dominik; Johnson, Charles; Koretsune, Takashi; Ibanez-Azpiroz, Julen; Lee, Hyungjun; Lihm, Jae-Mo; Marchand, Daniel; Marrazzo, Antimo; Mokrousov, Yuriy; Mustafa, Jamal I.; Nohara, Yoshiro; Nomura, Yusuke; Paulatto, Lorenzo; Ponce, Samuel; Ponweiser, Thomas; Qiao, Junfeng; Thole, Florian; Tsirkin, Stepan S.; Wierzbowska, Malgorzata; Marzari, Nicola; Vanderbilt, David; Souza, Ivo; Mostofi, Arash A.; Yates, Jonathan R.
    Journal of Physics: Condensed Matter (2020), 32 (16), 165902CODEN: JCOMEL; ISSN:0953-8984. (IOP Publishing Ltd.)
    Wannier90 is an open-source computer program for calcg. maximally-localized Wannier functions (MLWFs) from a set of Bloch states. It is interfaced to many widely used electronic-structure codes thanks to its independence from the basis sets representing these Bloch states. In the past few years the development of Wannier90 has transitioned to a community-driven model; this has resulted in a no. of new developments that have been recently released in Wannier90 v3.0. In this article we describe these new functionalities, that include the implementation of new features for wannierisation and disentanglement (symmetry-adapted Wannier functions, selectively-localized Wannier functions, selected columns of the d. matrix) and the ability to calc. new properties (shift currents and Berry-curvature dipole, and a new interface to many-body perturbation theory); performance improvements, including parallelization of the core code; enhancements in functionality (support for spinor-valued Wannier functions, more accurate methods to interpolate quantities in the Brillouin zone); improved usability (improved plotting routines, integration with high-throughput automation frameworks), as well as the implementation of modern software engineering practices (unit testing, continuous integration, and automatic source-code documentation). These new features, capabilities, and code development model aim to further sustain and expand the community uptake and range of applicability, that nowadays spans complex and accurate dielec., electronic, magnetic, optical, topol. and transport properties of materials.
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  30. 30
    Wu, Q.; Zhang, S.; Song, H.-F.; Troyer, M.; Soluyanov, A. A. Wanniertools: An Open-Source Software Package for Novel Topological Materials. Comput. Phys. Commun. 2018, 224, 405– 416,  DOI: 10.1016/j.cpc.2017.09.033
    [Crossref], [CAS], Google Scholar
    30
    WannierTools : An open-source software package for novel topological materials
    Wu, QuanSheng; Zhang, ShengNan; Song, Hai-Feng; Troyer, Matthias; Soluyanov, Alexey A.
    Computer Physics Communications (2018), 224 (), 405-416CODEN: CPHCBZ; ISSN:0010-4655. (Elsevier B.V.)
    We present an open-source software package WannierTools, a tool for investigation of novel topol. materials. This code works in the tight-binding framework, which can be generated by another software package Wannier90 (Mostofi et al., 2008). It can help to classify the topol. phase of a given material by calcg. the Wilson loop, and can get the surface state spectrum, which is detected by angle resolved photoemission (ARPES) and in scanning tunneling microscopy (STM) expts. It also identifies positions of Weyl/Dirac points and nodal line structures, calcs. the Berry phase around a closed momentum loop and Berry curvature in a part of the Brillouin zone (BZ).Program title:WannierToolsProgram Files doi:http://dx.doi.org/10.17632/ygsmh4hyh6.1Licensing provisions: GNU General Public Licence 3.0Programming language: Fortran 90External routines/libraries used:BLAS (http://www/netlib.org/blas)LAPACK (http://www.netlib.org/lapack)Nature of problem: Identifying topol. classifications of cryst. systems including insulators, semimetals, metals, and studying the electronic properties of the related slab and ribbon systems.Soln. method: Tight-binding method is a good approxn. for solid systems. Based on that, Wilson loop is used for topol. phase classification. The iterative Green's function is used for obtaining the surface state spectrum.
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  31. 31
    He, W.-Y.; Xu, X. Y.; Law, K. T. Kramers Weyl Semimetals as Quantum Solenoids and Their Applications in Spin-Orbit Torque Devices. Commun. Phys. 2021, 4, 1– 8,  DOI: 10.1038/s42005-021-00564-w
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  32. 32
    Hafner, J. Ab-Initio Simulations of Materials Using Vasp: Density-Functional Theory and Beyond. J. Comput. Chem. 2008, 29, 2044– 2078,  DOI: 10.1002/jcc.21057
    [Crossref], [PubMed], [CAS], Google Scholar
    32
    Ab-initio simulations of materials using VASP: density-functional theory and beyond
    Hafner, Juergen
    Journal of Computational Chemistry (2008), 29 (13), 2044-2078CODEN: JCCHDD; ISSN:0192-8651. (John Wiley & Sons, Inc.)
    A review. During the past decade, computer simulations based on a quantum-mech. description of the interactions between electrons and between electrons and at. nuclei have developed an increasingly important impact on solid-state physics and chem. and on materials science-promoting not only a deeper understanding, but also the possibility to contribute significantly to materials design for future technologies. This development is based on two important columns: (i) The improved description of electronic many-body effects within d.-functional theory (DFT) and the upcoming post-DFT methods. (ii) The implementation of the new functionals and many-body techniques within highly efficient, stable, and versatile computer codes, which allow to exploit the potential of modern computer architectures. In this review, I discuss the implementation of various DFT functionals [local-d. approxn. (LDA), generalized gradient approxn. (GGA), meta-GGA, hybrid functional mixing DFT, and exact (Hartree-Fock) exchange] and post-DFT approaches [DFT + U for strong electronic correlations in narrow bands, many-body perturbation theory (GW) for quasiparticle spectra, dynamical correlation effects via the adiabatic-connection fluctuation-dissipation theorem (AC-FDT)] in the Vienna ab initio simulation package VASP. VASP is a plane-wave all-electron code using the projector-augmented wave method to describe the electron-core interaction. The code uses fast iterative techniques for the diagonalization of the DFT Hamiltonian and allows to perform total-energy calcns. and structural optimizations for systems with thousands of atoms and ab initio mol. dynamics simulations for ensembles with a few hundred atoms extending over several tens of ps. Applications in many different areas (structure and phase stability, mech. and dynamical properties, liqs., glasses and quasicrystals, magnetism and magnetic nanostructures, semiconductors and insulators, surfaces, interfaces and thin films, chem. reactions, and catalysis) are reviewed.
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  33. 33
    Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized Gradient Approximation Made Simple. Phys. Rev. Lett. 1996, 77, 3865– 3868,  DOI: 10.1103/PhysRevLett.77.3865
    [Crossref], [PubMed], [CAS], Google Scholar
    33
    Generalized gradient approximation made simple
    Perdew, John P.; Burke, Kieron; Ernzerhof, Matthias
    Physical Review Letters (1996), 77 (18), 3865-3868CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)
    Generalized gradient approxns. (GGA's) for the exchange-correlation energy improve upon the local spin d. (LSD) description of atoms, mols., and solids. We present a simple derivation of a simple GGA, in which all parameters (other than those in LSD) are fundamental consts. Only general features of the detailed construction underlying the Perdew-Wang 1991 (PW91) GGA are invoked. Improvements over PW91 include an accurate description of the linear response of the uniform electron gas, correct behavior under uniform scaling, and a smoother potential.
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  34. 34
    Kresse, G.; Joubert, D. From Ultrasoft Pseudopotentials to the Projector Augmented-Wave Method. Phys. Rev. B 1999, 59, 1758– 1775,  DOI: 10.1103/PhysRevB.59.1758
    [Crossref], [CAS], Google Scholar
    34
    From ultrasoft pseudopotentials to the projector augmented-wave method
    Kresse, G.; Joubert, D.
    Physical Review B: Condensed Matter and Materials Physics (1999), 59 (3), 1758-1775CODEN: PRBMDO; ISSN:0163-1829. (American Physical Society)
    The formal relationship between ultrasoft (US) Vanderbilt-type pseudopotentials and Blochl's projector augmented wave (PAW) method is derived. The total energy functional for US pseudopotentials can be obtained by linearization of two terms in a slightly modified PAW total energy functional. The Hamilton operator, the forces, and the stress tensor are derived for this modified PAW functional. A simple way to implement the PAW method in existing plane-wave codes supporting US pseudopotentials is pointed out. In addn., crit. tests are presented to compare the accuracy and efficiency of the PAW and the US pseudopotential method with relaxed-core all-electron methods. These tests include small mols. (H2, H2O, Li2, N2, F2, BF3, SiF4) and several bulk systems (diamond, Si, V, Li, Ca, CaF2, Fe, Co, Ni). Particular attention is paid to the bulk properties and magnetic energies of Fe, Co, and Ni.
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  • Abstract

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    Figure 1

    Figure 1. Crystal structure and electronic band structure of bulk CdAs2. (a) Optimized primitive (left) and conventional (right) unit cells of CdAs2. (b) First Brillouin zone of the primitive cell. (c) Calculated electronic band structure without SOC effects. (d) Calculated electronic band structure including SOC effects. The Fermi level is set to zero and marked by a horizontal red dashed line. Cd and As atoms are represented by yellow and purple balls, respectively. The Kramers–Weyl nodes (d) are marked by yellow circles.

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    Figure 2

    Figure 2. Characterization of the CdAs2 single crystal. (a) High-resolution transmission electron microscopy (HR-TEM) image showing the crystalline structure of CdAs2. (b) Small-area electron diffraction (SAED) pattern confirming the single crystal nature of CdAs2, although the existence of elongated spots is a fingerprint of a slight mosaicity. (c) X-ray diffraction (XRD) pattern revealing the high quality of the crystal with sharp Bragg peaks. (d) Temperature-dependent magnetoresistance curve of CdAs2 single crystal showing a linear dependence at low temperatures and a saturation behavior at high temperatures.

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    Figure 3

    Figure 3. Top (left panel) and side (right panel) view of (2 × 1) (top panel) and (3 × 1) (bottom panel) supercell of (a) As–S1, (b) As–S2, (c) Cd–S1, and (d) Cd–S2, respectively. Lighter colors represent lower atoms for better visualization of surface atoms.

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    Figure 4

    Figure 4. (a) Fermi surface of CdAs2 showing the electron pockets of the conduction band at the Fermi level, covering several Brillouin zones. (b) Constant energy surface at 1 eV and (c) 2.35 eV below the Fermi level illustrating the valence band structure evolution at higher k-values. The measurements were carried out at 40 K using hν = 100 eV photons in horizontal polarization setups. On the constant energy cuts, the projection of the Wigner–Seitz cells were overlaid and high-symmetry points were marked.

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    Figure 5

    Figure 5. Experimental band structure of bulk CdAs2 along various high-symmetry directions. (a) ARPES repeated along the X–M–X path, showing a large view of the valence band structure. (b) Second derivative plot to aid the visualization of the states. (c) Zoomed-in view of part a near the Fermi level, highlighting the pockets belonging to the conduction band manifold. (d) ARPES valence band structure measured along the Z–M–Z path (negative kx values). (e) Corresponding second derivative plot. The Z–M–Z path was also collected at positive kx values and shown in part f along with the (g) second derivative. The valence band was also measured along the (h, i) P–X–P path and (j, k) Z–P direction.

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    1. 1
      Kang, L.; Cao, Z. Y.; Wang, B. Pressure-Induced Electronic Topological Transition and Superconductivity in Topological Insulator Bi2Te2.1Se0.9. J. Phys. Chem. Lett. 2022, 13, 11521– 11527,  DOI: 10.1021/acs.jpclett.2c02981
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      1
      Pressure-Induced Electronic Topological Transition and Superconductivity in Topological Insulator Bi2Te2.1Se0.9
      Kang, Lei; Cao, Zi-Yu; Wang, Bo
      Journal of Physical Chemistry Letters (2022), 13 (49), 11521-11527CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
      One approach to discovering topol. superconductors is establishing supercond. based on well-identified topol. insulators. However, the coexistence of supercond. and a topol. state is always arcane. In this paper, we report how pressure tunes the crystal structure, electronic structure, and supercond. in topol. insulator Bi2Te2.1Se0.9. At ~ 2.5 GPa, the abnormal changes in c/a and the full width at half-max. of the A1g1 mode indicate the occurrence of an electronic topol. transition. The pressure-induced supercond. in Bi2Te2.1Se0.9 pinned with an electronic topol. transition presents at 2.4 GPa, which is far below the structural phase transition pressure of 8.4 GPa. These results suggest that the appearance of an electronic topol. transition is closely correlated with supercond. in the initial phase, where the topol. surface state persists. Our work clarifies the complex electronic structure of Bi2Te2.1Se0.9 and sheds light on the mechanism for supercond. in topol. insulators.
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    2. 2
      Kirby, R. J.; Scholes, G. D.; Schoop, L. M. Square-Net Topological Semimetals: How Spectroscopy Furthers Understanding and Control. J. Phys. Chem. Lett. 2022, 13, 838– 850,  DOI: 10.1021/acs.jpclett.1c03798
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      2
      Square-Net Topological Semimetals: How Spectroscopy Furthers Understanding and Control
      Kirby, Robert J.; Scholes, Gregory D.; Schoop, Leslie M.
      Journal of Physical Chemistry Letters (2022), 13 (3), 838-850CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
      A review. Square-net materials are well positioned to lead optical spectroscopic explorations into the electronic structure, photoinduced dynamics, and phase transitions in topol. semimetals. Hundreds of square-net topol. semimetals can be prepd. that have remarkably different electronic and optical properties despite having similar structures. Here we present what has been gleaned recently from these materials with the whole gamut of optical spectroscopies, ranging from steady-state reflectance and Raman investigations into topol. band structures, electronic correlations, and equil. phase transitions to time-resolved techniques used to decipher ultrafast relaxation dynamics and nonequil. photoinduced phase transitions. We end with a discussion of some major remaining questions and possible future research directions.
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    3. 3
      Klimovskikh, I. I.; Estyunin, D. A.; Makarova, T. P.; Tereshchenko, O. E.; Kokh, K. A.; Shikin, A. M. Electronic Structure of Pb Adsorbed Surfaces of Intrinsic Magnetic Topological Insulators. J. Phys. Chem. Lett. 2022, 13, 6628– 6634,  DOI: 10.1021/acs.jpclett.2c01245
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      3
      Electronic structure of Pb adsorbed surfaces of intrinsic magnetic topological insulators
      Klimovskikh, Ilya I.; Estyunin, Dmitry A.; Makarova, Tatyana P.; Tereshchenko, Oleg E.; Kokh, Konstantin A.; Shikin, Alexander M.
      Journal of Physical Chemistry Letters (2022), 13 (29), 6628-6634CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
      Recently discovered intrinsic magnetic topol. insulators (IMTIs) constitute a unique class of quantum materials that combine magnetism and nontrivial topol. One of the most promising applications of these materials is Majorana fermion creation; Majorana fermions are expected to arise when a superconductor is in contact with the surface of an IMTI. Here we study the adsorption of Pb ultrathin films on top of IMTIs of various stoichiometries. By means of XPS we figure out the formation of the Pb wetting layer coupled to the surface atoms for low coverages and overlayer growth on top upon further deposition. Investigation of the adsorbed surfaces by means of ARPES shows the Dirac cone survival, its shift in a binding energy, and the Pb electronic states appearance. The obtained results allow the Pb/IMTI interfaces to be constructed for the understanding of the proximity effect and provide an important step toward quantum device engineering based on IMTIs.
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    4. 4
      Li, L.; Gunasekaran, S.; Wei, Y.; Nuckolls, C.; Venkataraman, L. Reversed Conductance Decay of 1d Topological Insulators by Tight-Binding Analysis. J. Phys. Chem. Lett. 2022, 13, 9703– 9710,  DOI: 10.1021/acs.jpclett.2c02812
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      4
      Reversed Conductance Decay of One-Dimensional Topological Insulators by Tight-Binding Analysis
      Li, Liang; Gunasekaran, Suman; Wei, Yujing; Nuckolls, Colin; Venkataraman, Latha
      Journal of Physical Chemistry Letters (2022), 13 (41), 9703-9710CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
      Reversed conductance decay describes increasing conductance of a mol. chain series with increasing chain length. Realizing reversed conductance decay is an important step toward making long and highly conducting mol. wires. Recent work has shown that one-dimensional topol. insulators (1D TIs) can exhibit reversed conductance decay due to their nontrivial edge states. The Su-Schrieffer-Heeger (SSH) model for 1D TIs relates to the electronic structure of these isolated mols. but not their electron transport properties as single-mol. junctions. Herein, we use a tight-binding approach to demonstrate that polyacetylene and other diradicaloid 1D TIs show a reversed conductance decay at the short chain limit. We explain these conductance trends by analyzing the impact of the edge states in these 1D systems on the single-mol. junction transmission. Addnl., we discuss how the self-energy from the electrode-mol. coupling and the on-site energy of the edge sites can be tuned to create longer wires with reversed conductance decays.
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    5. 5
      Li, Y.; Zhang, Y. F.; Deng, J.; Dong, W. H.; Sun, J. T.; Pan, J.; Du, S. Rational Design of Heteroanionic Two-Dimensional Materials with Emerging Topological, Magnetic, and Dielectric Properties. J. Phys. Chem. Lett. 2022, 13, 3594– 3601,  DOI: 10.1021/acs.jpclett.2c00620
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      5
      Rational Design of Heteroanionic Two-Dimensional Materials with Emerging Topological, Magnetic, and Dielectric Properties
      Li, Yuhui; Zhang, Yan-Fang; Deng, Jun; Dong, Wen-Han; Sun, Jia-Tao; Pan, Jinbo; Du, Shixuan
      Journal of Physical Chemistry Letters (2022), 13 (16), 3594-3601CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
      Designing and tuning the phys. properties of two-dimensional (2D) materials at the at. level are crucial to the development of 2D technologies. Here, we introduce heteroanions into metal-centered octahedral structural units of a 2D crystal breaking the Oh symmetry, together with the synergistic effect of anions' electrons and electronegativity, to realize ternary 2D materials with emerging topol., magnetic, and dielec. properties. Using an intrinsic heteroanionic van der Waals layered material, VOCl, as a prototype, 20 2D monolayers VXY (X = B, C, N, O, or F; Y = F, Cl, Br, or I) are obtained and investigated by means of first-principles calcns. The anion engineering in this family significantly reshapes the electronic properties of VOCl, leading to nonmagnetic topol. insulators with nontrivial edge states in VCY, ferromagnetic half-semimetals with a nodal ring around the Fermi energy in VNY, and insulators with dielec. consts. in VOY higher than that of h-BN. This work demonstrates the rationality and validity of the design strategy of multiple-anion engineering to achieve superior properties in the 2D monolayers with potential application in electronics and spintronics.
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    6. 6
      Liang, Y.; Zheng, F.; Zhao, P.; Wang, Q.; Frauenheim, T. Intrinsic Ferroelectric Quantum Spin Hall Insulator in Monolayer Na3Bi with Surface Trimerization. J. Phys. Chem. Lett. 2022, 13, 11059– 11064,  DOI: 10.1021/acs.jpclett.2c03270
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      6
      Intrinsic ferroelectric quantum spin Hall insulator in monolayer Na3Bi with surface trimerization
      Liang, Yan; Zheng, Fulu; Zhao, Pei; Wang, Qiang; Frauenheim, Thomas
      Journal of Physical Chemistry Letters (2022), 13 (48), 11059-11064CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
      Two-dimensional (2D) ferroelec. quantum spin Hall (FEQSH) insulator, which features coexisting ferroelec. and topol. insulating orders in two-dimension, is generally considered available only in engineered 2D systems. This is detrimental to the synthesis and application of next generation nonvolatile functional candidates. Therefore, exploring the intrinsic 2D FEQSH insulator is crucial. Here, by means of first-principles, we report a long-thought intrinsic 2D FEQSH insulator in monolayer Na3Bi with surface trimerization. The material harbors merits including large ferroelec. polarization, sizable nontrivial band gap, and low switching barrier, which are particularly beneficial for the detection and observation of ferroelec. topol. insulating states. Also, it is capable of nonvolatile switching of nontrivial spin textures via inherent ferroelectricity. The fantastic combination of excellent ferroelec. and topol. phases in intrinsic the Na3Bi monolayer serves as an alluring platform for accelerating both scientific discoveries and innovative applications.
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    7. 7
      Xi, M.; Chen, F.; Gong, C.; Tian, S.; Yin, Q.; Qian, T.; Lei, H. Relationship between Antisite Defects, Magnetism, and Band Topology in MnSb2Te4 Crystals with Tc≈ 40 K. J. Phys. Chem. Lett. 2022, 13, 10897– 10904,  DOI: 10.1021/acs.jpclett.2c02775
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      7
      Relationship between Antisite Defects, Magnetism, and Band Topology in MnSb2Te4 Crystals with TC ≈ 40 K
      Xi, Ming; Chen, Famin; Gong, Chunsheng; Tian, Shangjie; Yin, Qiangwei; Qian, Tian; Lei, Hechang
      Journal of Physical Chemistry Letters (2022), 13 (47), 10897-10904CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
      MnSb2Te4 has attracted extensive attention because of its rich and adjustable magnetic properties. Here, using a modified crystal growth method, ferrimagnetic MnSb2Te4 crystals with enhanced Curie temp. (TC) of about 40 K with dominant hole-type carriers and intrinsic anomalous Hall effect is obtained. Time- and angle-resolved photoemission spectroscopy reveals that surface states are absent in both antiferromagnetic and ferrimagnetic MnSb2Te4, implying that they have topol. trivial electronic structures. We propose that the enhancement of ferrimagnetism mainly originates from the increase of intralayer magnetic coupling caused by the decrease of Sb content at Mn sites when the decrease of Mn concn. at Sb sites would prefer the nontrival band topol. Moreover, it is known that the initial satn. moment (Mis) is sensitive to the concns. of Mn/Sb antisite defects; thus, the Mis could be a valuable parameter to evaluate the magnetic and topol. properties of MnX2nTe3n+1 (X = Bi, Sb) families.
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    8. 8
      Yakovlev, D. S.; Lvov, D. S.; Emelyanova, O. V.; Dzhumaev, P. S.; Shchetinin, I. V.; Skryabina, O. V.; Egorov, S. V.; Ryazanov, V. V.; Golubov, A. A.; Roditchev, D.; Stolyarov, V. S. Physical Vapor Deposition Features of Ultrathin Nanocrystals of Bi2(TexSe1-X)3. J. Phys. Chem. Lett. 2022, 13, 9221– 9231,  DOI: 10.1021/acs.jpclett.2c02664
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      8
      Physical Vapor Deposition Features of Ultrathin Nanocrystals of Bi2(TexSe1-x)3
      Yakovlev, Dmitry S.; Lvov, Dmitry S.; Emelyanova, Olga V.; Dzhumaev, Pave S.; Shchetinin, Igor V.; Skryabina, Olga V.; Egorov, Sergey V.; Ryazanov, Valery V.; Golubov, Alexander A.; Roditchev, Dimitri; Stolyarov, Vasily S.
      Journal of Physical Chemistry Letters (2022), 13 (39), 9221-9231CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
      Structural and electronic properties of ultrathin nanocrystals of chalcogenide Bi2(Tex Se1-x)3 were studied. The nanocrystals were formed from the parent compd. Bi2Te2Se on as-grown and thermally oxidized Si(100) substrates using Ar-assisted phys. vapor deposition, resulting in well-faceted single crystals several quintuple layers thick and a few hundreds nanometers large. The chem. compn. and structure of the nanocrystals were analyzed by energy-dispersive X-ray spectroscopy, XPS, electron backscattering, and X-ray diffraction. The electron transport through nanocrystals connected to superconducting Nb electrodes demonstrated Josephson behavior, with the predominance of the topol. channels []. The present paper focuses on the effect of the growth conditions on the morphol., structural, and electronic properties of nanocrystals.
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    9. 9
      (a) Zhou, Z.; Peng, K.; Xiao, S.; Wei, Y.; Dai, Q.; Lu, X.; Wang, G.; Zhou, X. Anomalous Thermoelectric Performance in Asymmetric Dirac Semimetal BaAgBi. J. Phys. Chem. Lett. 2022, 13, 2291– 2298,  DOI: 10.1021/acs.jpclett.2c00379
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      9a
      Anomalous Thermoelectric Performance in Asymmetric Dirac Semimetal BaAgBi
      Zhou, Zizhen; Peng, Kunling; Xiao, Shijuan; Wei, Yiqing; Dai, Qinjin; Lu, Xu; Wang, Guoyu; Zhou, Xiaoyuan
      Journal of Physical Chemistry Letters (2022), 13 (10), 2291-2298CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
      Multiple-band degeneracy has been widely recognized to be beneficial for high thermoelec. performance. Here, we discover that the p-type Dirac bands with lower degeneracy synergistically produce a higher Seebeck coeff. and elec. cond. in topol. semimetal BaAgBi. The anomalous transport phenomenon intrinsically originated from the asym. electronic structures: (i) complete p-type Dirac bands near the Fermi level facilitate high and strong energy-dependent hole relaxation time; (ii) the presence of addnl. parabolic conduction valleys allows for a large d. of states to accept scattered electrons, leading to an enlarged hole-electron relaxation time ratio and, thus, weakened bipolar effect. In combination with the strong lattice anharmonicity, an exceptional p-type av. ZT of 0.42 is achieved from 300 to 600 K, which can be dramatically enhanced to 1.38 via breaking the C3v symmetry. This work uncovers the underlying mechanisms governing the abnormal transport behavior in Dirac semimetal BaAgBi and highlights the asym. electronic structures as target features to discover/design high-performance thermoelec. materials.
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      .
      (b) Borca, B.; Michnowicz, T.; Aguilar-Galindo, F.; Pétuya, R.; Pristl, M.; Schendel, V.; Pentegov, I.; Kraft, U.; Klauk, H.; Wahl, P. Chiral and Catalytic Effects of Site-Specific Molecular Adsorption. J. Phys. Chem. Lett. 2023, 14 (8), 2072– 2077,  DOI: 10.1021/acs.jpclett.2c03575
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      9b
      Chiral and Catalytic Effects of Site-Specific Molecular Adsorption
      Borca, Bogdana; Michnowicz, Tomasz; Aguilar-Galindo, Fernando; Petuya, Remi; Pristl, Marcel; Schendel, Verena; Pentegov, Ivan; Kraft, Ulrike; Klauk, Hagen; Wahl, Peter; Arnau, Andres; Schlickum, Uta
      Journal of Physical Chemistry Letters (2023), 14 (8), 2072-2077CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
      The changes of properties and preferential interactions based on subtle energetic differences are important characteristics of org. mols., particularly for their functionalities in biol. systems. Only slightly energetically favored interactions are important for the mol. adsorption and bonding to surfaces, which define their properties for further technol. applications. Here, prochiral tetracenothiophene mols. are adsorbed on the Cu(111) surface. The chiral adsorption configurations are detd. by Scanning Tunneling Microscopy studies and confirmed by 1st-principles calcns. Remarkably, the selection of the adsorption sites by chem. different moieties of the mols. is dictated by the arrangement of the atoms in the 1st and 2nd surface layers. Also, the authors have studied the thermal effects on the direct desulfurization reaction that occurs under the catalytic activity of the Cu substrate. This reaction leads to a product that is covalently bound to the surface in chiral configurations.
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    10. 10
      Sanchez, D. S.; Belopolski, I.; Cochran, T. A.; Xu, X.; Yin, J.-X.; Chang, G.; Xie, W.; Manna, K.; Süß, V.; Huang, C.-Y. Topological Chiral Crystals with Helicoid-Arc Quantum States. Nature 2019, 567, 500– 505,  DOI: 10.1038/s41586-019-1037-2
      [Crossref], [PubMed], [CAS], Google Scholar
      10
      Topological chiral crystals with helicoid-arc quantum states
      Sanchez, Daniel S.; Belopolski, Ilya; Cochran, Tyler A.; Xu, Xitong; Yin, Jia-Xin; Chang, Guoqing; Xie, Weiwei; Manna, Kaustuv; Suss, Vicky; Huang, Cheng-Yi; Alidoust, Nasser; Multer, Daniel; Zhang, Songtian S.; Shumiya, Nana; Wang, Xirui; Wang, Guang-Qiang; Chang, Tay-Rong; Felser, Claudia; Xu, Su-Yang; Jia, Shuang; Lin, Hsin; Hasan, M. Zahid
      Nature (London, United Kingdom) (2019), 567 (7749), 500-505CODEN: NATUAS; ISSN:0028-0836. (Nature Research)
      The quantum behavior of electrons in materials is the foundation of modern electronics and information technol., and quantum materials with topol. electronic and optical properties are essential for realizing quantized electronic responses that can be used for next generation technol. Here, the authors report the first observation of topol. quantum properties of chiral crystals in the RhSi family. The authors find that this material class hosts a quantum phase of matter that exhibits nearly ideal topol. surface properties originating from the crystals' structural chirality. Electrons on the surface of these crystals show a highly unusual helicoid fermionic structure that spirals around two high-symmetry momenta, indicating electronic topol. chirality. The existence of bulk multiply degenerate band fermions is guaranteed by the crystal symmetries; however, to det. the topol. invariant or charge in these chiral crystals, it is essential to identify and study the helicoid topol. of the arc states. The helicoid arcs that the authors observe on the surface characterize the topol. charges of ±2, which arise from bulk higher-spin chiral fermions. These topol. conductors exhibit giant Fermi arcs of max. length (π), which are orders of magnitude larger than those found in known chiral Weyl fermion semimetals. The results demonstrate an electronic topol. state of matter on structurally chiral crystals featuring helicoid-arc quantum states. Such exotic multifold chiral fermion semimetal states could be used to detect a quantized photogalvanic optical response, the chiral magnetic effect and other optoelectronic phenomena predicted for this class of materials.
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    11. 11
      Chang, G.; Wieder, B. J.; Schindler, F.; Sanchez, D. S.; Belopolski, I.; Huang, S.-M.; Singh, B.; Wu, D.; Chang, T.-R.; Neupert, T.; Xu, S.-Y.; Lin, H.; Hasan, M. Z. Topological Quantum Properties of Chiral Crystals. Nat. Mater. 2018, 17, 978– 985,  DOI: 10.1038/s41563-018-0169-3
      [Crossref], [PubMed], [CAS], Google Scholar
      11
      Topological quantum properties of chiral crystals
      Chang, Guoqing; Wieder, Benjamin J.; Schindler, Frank; Sanchez, Daniel S.; Belopolski, Ilya; Huang, Shin-Ming; Singh, Bahadur; Wu, Di; Chang, Tay-Rong; Neupert, Titus; Xu, Su-Yang; Lin, Hsin; Hasan, M. Zahid
      Nature Materials (2018), 17 (11), 978-985CODEN: NMAACR; ISSN:1476-1122. (Nature Research)
      Chiral crystals are materials with a lattice structure that has a well-defined handedness due to the lack of inversion, mirror or other roto-inversion symmetries. Although it has been shown that the presence of cryst. symmetries can protect topol. band crossings, the topol. electronic properties of chiral crystals remain largely uncharacterized. Here we show that Kramers-Weyl fermions are a universal topol. electronic property of all non-magnetic chiral crystals with spin-orbit coupling and are guaranteed by structural chirality, lattice translation and time-reversal symmetry. Unlike conventional Weyl fermions, they appear at time-reversal-invariant momenta. We identify representative chiral materials in 33 of the 65 chiral space groups in which Kramers-Weyl fermions are relevant to the low-energy physics. We det. that all point-like nodal degeneracies in non-magnetic chiral crystals with relevant spin-orbit coupling carry non-trivial Chern nos. Kramers-Weyl materials can exhibit a monopole-like electron spin texture and topol. non-trivial bulk Fermi surfaces over an unusually large energy window.
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    12. 12
      Hasan, M. Z.; Chang, G.; Belopolski, I.; Bian, G.; Xu, S.-Y.; Yin, J.-X. Weyl, Dirac and High-Fold Chiral Fermions in Topological Quantum Matter. Nat. Rev. Mater. 2021, 6, 784– 803,  DOI: 10.1038/s41578-021-00301-3
      [Crossref], [CAS], Google Scholar
      12
      Weyl, Dirac and high-fold chiral fermions in topological quantum matter
      Hasan, M. Zahid; Chang, Guoqing; Belopolski, Ilya; Bian, Guang; Xu, Su-Yang; Yin, Jia-Xin
      Nature Reviews Materials (2021), 6 (9), 784-803CODEN: NRMADL; ISSN:2058-8437. (Nature Portfolio)
      A review Quantum materials hosting Weyl fermions have opened a new era of research in condensed matter physics. First proposed in 1929 in the context of particle physics, Weyl fermions have yet to be obsd. as elementary particles. In 2015, Weyl fermions were detected as collective electronic excitations in the strong spin-orbit coupled material tantalum arsenide, TaAs. This discovery was followed by a flurry of exptl. and theor. explorations of Weyl phenomena in materials. Weyl materials naturally lend themselves to the exploration of the topol. index assocd. with Weyl fermions and their divergent Berry curvature field, as well as the topol. bulk-boundary correspondence, giving rise to protected conducting surface states. Here, we review the broader class of Weyl topol. phenomena in materials, starting with the observation of emergent Weyl fermions in the bulk and Fermi arc states on the surface of the TaAs family of crystals by photoemission spectroscopy. We then discuss several exotic optical and magnetic responses obsd. in these materials, as well as progress in developing related chiral materials. We discuss the conceptual development of high-fold chiral fermions, which generalize Weyl fermions, and we review the observation of high-fold chiral fermion phases by taking the rhodium silicide, RhSi, family of crystals as a prime example. Lastly, we discuss recent advances in Weyl line phases in magnetic topol. materials. With this Review, we aim to provide an introduction to the basic concepts underlying Weyl physics in condensed matter, and to representative materials and their electronic structures and topol. as revealed by spectroscopic studies. We hope this work serves as a guide for future theor. and exptl. explorations of chiral fermions and related topol. quantum systems with potentially enhanced functionalities.
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    13. 13
      Tan, W.; Jiang, X.; Li, Y.; Wu, X.; Wang, J.; Huang, B. A Unified Understanding of Diverse Spin Textures of Kramers–Weyl Fermions in Nonmagnetic Chiral Crystals. Adv. Funct. Mater. 2022, 32, 2208023,  DOI: 10.1002/adfm.202208023
      [Crossref], [CAS], Google Scholar
      13
      A Unified Understanding of Diverse Spin Textures of Kramers-Weyl Fermions in Nonmagnetic Chiral Crystals
      Tan, Wei; Jiang, Xiao; Li, Yang; Wu, Xiaoqiang; Wang, Jianfeng; Huang, Bing
      Advanced Functional Materials (2022), 32 (49), 2208023CODEN: AFMDC6; ISSN:1616-301X. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Chiral crystals, characterized by rotation, screw rotation, and translation symmetries are abundant in nature. The existence of Kramers-Weyl fermions (KWFs) at the time-reversal-invariant momenta in nonmagnetic chiral crystals (NCCs) has attracted intense attention due to their unique phys. properties beyond conventional Weyl fermions. Although the spin texture, one of the most fundamental phys. quantities, is found to be dramatically different for different KWFs in different NCCs, a unified understanding of this puzzling phenomenon is still lacking. In this article, combining k · p theory and first-principles calcns., k-linear Hamiltonians for KWFs are constructed and consequently a complete classification for the spin textures of KWFs in all the NCCs is made, which are confirmed by a series of material example calcns. Interestingly, it is found that the spin textures are reversed in NCCs with opposite chirality, leading to reversed Fermi arc surface states. Importantly, this study unveils that the nonlinear optical responses around the KWFs in NCCs can be largely detd. by their spin texture classification. This study not only provides a unified understanding of the spin textures of KWFs in all the NCCs, but also suggests a principle to design novel KWF-related spintronics and nonlinear optics.
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    14. 14
      Shekhar, C. Chirality Meets Topology. Nat. Mater. 2018, 17, 953– 954,  DOI: 10.1038/s41563-018-0210-6
      [Crossref], [PubMed], [CAS], Google Scholar
      14
      Chirality meets topology
      Shekhar, Chandra
      Nature Materials (2018), 17 (11), 953-954CODEN: NMAACR; ISSN:1476-1122. (Nature Research)
      By considering the topol. of chiral crystals, a new type of massless fermion, connected with giant arc-like surface states, are predicted. Such Kramers-Weyl fermions should manifest themselves in a wide variety of chiral materials.
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      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXitVSlsL%252FK&md5=4cfdc8ad569b2d706c632dd8fdce438b
    15. 15
      Chang, G.; Xu, S.-Y.; Wieder, B. J.; Sanchez, D. S.; Huang, S.-M.; Belopolski, I.; Chang, T.-R.; Zhang, S.; Bansil, A.; Lin, H. Unconventional Chiral Fermions and Large Topological Fermi Arcs in RhSi. Phys. Rev. Lett. 2017, 119, 206401,  DOI: 10.1103/PhysRevLett.119.206401
      [Crossref], [PubMed], [CAS], Google Scholar
      15
      Unconventional chiral fermions and large topological Fermi arcs in RhSi
      Chang, Guoqing; Xu, Su-Yang; Wieder, Benjamin J.; Sanchez, Daniel S.; Huang, Shin-Ming; Belopolski, Ilya; Chang, Tay-Rong; Zhang, Songtian; Bansil, Arun; Lin, Hsin; Hasan, M. Zahid
      Physical Review Letters (2017), 119 (20), 206401/1-206401/6CODEN: PRLTAO; ISSN:1079-7114. (American Physical Society)
      A review. The theor. proposal of chiral fermions in topol. semimetals has led to a significant effort towards their exptl. realization. In particular, the Fermi surfaces of chiral semimetals carry quantized Chern nos., making them an attractive platform for the observation of exotic transport and optical phenomena. While the simplest example of a chiral fermion in condensed matter is a conventional |C| = 1 Weyl fermion, recent theor. works have proposed a no. of unconventional chiral fermions beyond the std. model which are protected by unique combinations of topol. and cryst. symmetries. However, materials candidates for exptl. probing the transport and response signatures of these unconventional fermions have thus far remained elusive. In this Letter, we propose the RhSi family in space group No. 198 as the ideal platform for the exptl. examn. of unconventional chiral fermions. We find that RhSi is a filling-enforced semimetal that features near its Fermi surface a chiral double sixfold-degenerate spin-1 Weyl node at R and a previously uncharacterized fourfold-degenerate chiral fermion at Γ. Each unconventional fermion displays Chern no. ±4 at the Fermi level. We also show that RhSi displays the largest possible momentum sepn. of compensative chiral fermions, the largest proposed topol. nontrivial energy window, and the longest possible Fermi arcs on its surface. We conclude by proposing signatures of an exotic bulk photogalvanic response in RhSi.
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    16. 16
      Arnold, F.; Shekhar, C.; Wu, S.-C.; Sun, Y.; Dos Reis, R. D.; Kumar, N.; Naumann, M.; Ajeesh, M. O.; Schmidt, M.; Grushin, A. G. Negative Magnetoresistance without Well-Defined Chirality in the Weyl Semimetal TaP. Nat. Commun. 2016, 7, 1– 7,  DOI: 10.1038/ncomms11615
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    17. 17
      Tang, P.; Zhou, Q.; Zhang, S.-C. Multiple Types of Topological Fermions in Transition Metal Silicides. Phys. Rev. Lett. 2017, 119, 206402,  DOI: 10.1103/PhysRevLett.119.206402
      [Crossref], [PubMed], [CAS], Google Scholar
      17
      Multiple types of topological fermions in transition metal silicides
      Tang, Peizhe; Zhou, Quan; Zhang, Shou-Cheng
      Physical Review Letters (2017), 119 (20), 206402/1-206402/6CODEN: PRLTAO; ISSN:1079-7114. (American Physical Society)
      A review. Exotic massless fermionic excitations with nonzero Berry flux, other than the Dirac and Weyl fermions, could exist in condensed matter systems under the protection of cryst. symmetries, such as spin-1 excitations with threefold degeneracy and spin-3/2 Rarita-Schwinger-Weyl fermions. Herein, by using the ab initio d. functional theory, we show that these unconventional quasiparticles coexist with type-I and type-II Weyl fermions in a family of transition metal silicides, including CoSi, RhSi, RhGe, and CoGe, when spin-orbit coupling is considered. Their nontrivial topol. results in a series of extensive Fermi arcs connecting projections of these bulk excitations on the side surface, which is confirmed by (001) surface electronic spectra of CoSi. In addn., these stable arc states exist within a wide energy window around the Fermi level, which makes them readily accessible in angle-resolved photoemission spectroscopy measurements.
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    18. 18
      Rikken, G.; Raupach, E. Observation of Magneto-Chiral Dichroism. Nature 1997, 390, 493– 494,  DOI: 10.1038/37323
      [Crossref], [CAS], Google Scholar
      18
      Observation of magneto-chiral dichroism
      Rikken, G. L. J. A.; Raupach, E.
      Nature (London) (1997), 390 (6659), 493-494CODEN: NATUAS; ISSN:0028-0836. (Macmillan Magazines)
      Magneto-chiral dichroism was obsd. and its enantioselectivity demonstrated in Eu[(±)tfd]3 (H(±)tfd = 3-trifluoroacetyl-(±)-camphor) in DMSO-d6.
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    19. 19
      Train, C.; Gheorghe, R.; Krstic, V.; Chamoreau, L.-M.; Ovanesyan, N. S.; Rikken, G. L.; Gruselle, M.; Verdaguer, M. Strong Magneto-Chiral Dichroism in Enantiopure Chiral Ferromagnets. Nat. Mater. 2008, 7, 729– 734,  DOI: 10.1038/nmat2256
      [Crossref], [PubMed], [CAS], Google Scholar
      19
      Strong magneto-chiral dichroism in enantiopure chiral ferromagnets
      Train, Cyrille; Gheorghe, Ruxandra; Krstic, Vojislav; Chamoreau, Lise-Marie; Ovanesyan, Nikolai S.; Rikken, Geert L. J. A.; Gruselle, Michel; Verdaguer, Michel
      Nature Materials (2008), 7 (9), 729-734CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)
      As materials science is moving towards the synthesis, the study and the processing of new materials exhibiting well-defined and complex functions, the synthesis of new multifunctional materials is one of the important challenges. One of these complex phys. properties is magneto-chiral dichroism which arises, at second order, from the coexistence of spatial asymmetry and magnetization in a material. Herein the authors report the first measurement of strong magneto-chiral dichroism in an enantiopure chiral ferromagnet. The ab initio synthesis of the enantiopure chiral ferromagnet is based on an enantioselective self-assembly, where a resolved chiral quaternary ammonium cation imposes the abs. configurations of the metal centers within Cr-Mn two-dimensional oxalate layers. The ferromagnetic interaction between Cr(III) and Mn(II) ions leads to a Curie temp. of 7 K. The magneto-chiral dichroic effect is enhanced by a factor of 17 when entering into the ferromagnetic phase. Magneto-chiral dichroism is an effect in which unpolarized light is absorbed differently for parallel and antiparallel propagation with respect to an applied magnetic field. Previous observations have only seen a rather weak demonstration of this effect. Following a challenging synthesis, strong magneto-dichroism has now been obsd. in enantiopure chiral ferromagnets. Magneto-chiral dichroism is an effect in which unpolarized light is absorbed differently for parallel and antiparallel propagation with respect to an applied magnetic field. Previous observations have only seen a rather weak demonstration of this effect. Following a challenging synthesis, strong magneto-dichroism has now been obsd. in enantiopure chiral ferromagnets.
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    20. 20
      Hannam, K.; Powell, D. A.; Shadrivov, I. V.; Kivshar, Y. S. Broadband Chiral Metamaterials with Large Optical Activity. Phys. Rev. B 2014, 89, 125105,  DOI: 10.1103/PhysRevB.89.125105
      [Crossref], [CAS], Google Scholar
      20
      Broadband chiral metamaterials with large optical activity
      Hannam, Kirsty; Powell, David A.; Shadrivov, Ilya V.; Kivshar, Yuri S.
      Physical Review B: Condensed Matter and Materials Physics (2014), 89 (12), 125105/1-125105/6CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)
      We study theor. and exptl. a type of metamaterial with hybrid elements composed of twisted pairs of cross-shaped meta-atoms and their complements. We reveal that such two-layer metasurfaces demonstrate large, dispersionless optical activity at the transmission resonance accompanied by very low ellipticity. We develop a retrieval procedure to det. the effective material parameters for this structure, which has symmetry (C4) of a lower order than other commonly studied chiral structures. We verify our theor. approach by reproducing numerical and exptl. scattering parameters.
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    21. 21
      Zhao, R.; Zhang, L.; Zhou, J.; Koschny, T.; Soukoulis, C. Conjugated Gammadion Chiral Metamaterial with Uniaxial Optical Activity and Negative Refractive Index. Phys. Rev. B 2011, 83, 035105,  DOI: 10.1103/PhysRevB.83.035105
      [Crossref], [CAS], Google Scholar
      21
      Conjugated gammadion chiral metamaterial with uniaxial optical activity and negative refractive index
      Zhao, R.; Zhang, L.; Zhou, J.; Koschny, Th.; Soukoulis, C. M.
      Physical Review B: Condensed Matter and Materials Physics (2011), 83 (3), 035105/1-035105/4CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)
      A conjugated gammadion chiral metamaterial that uniaxially exhibits huge optical activity and CD, and gives a neg. refractive index is demonstrated numerically and exptl. This chiral design provides smaller unit cell size and larger chirality compared with other published planar designs. Expts. are performed at GHz frequencies (around 6 GHz) and are in agreement with the numerical simulations.
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    22. 22
      Tokunaga, Y.; Yu, X.; White, J.; Rønnow, H. M.; Morikawa, D.; Taguchi, Y.; Tokura, Y. A New Class of Chiral Materials Hosting Magnetic Skyrmions Beyond Room Temperature. Nat. Commun. 2015, 6, 1– 7,  DOI: 10.1038/ncomms8638
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    23. 23
      Jena, J.; Göbel, B.; Ma, T.; Kumar, V.; Saha, R.; Mertig, I.; Felser, C.; Parkin, S. S. Elliptical Bloch Skyrmion Chiral Twins in an Antiskyrmion System. Nat. Commun. 2020, 11, 1– 9,  DOI: 10.1038/s41467-020-14925-6
      [Crossref], [PubMed], Google Scholar
      There is no corresponding record for this reference.
    24. 24
      Żdanowicz, E.; Wojciechowski, W.; Misiewicz, J.; Lisunov, K. Negative Magnetoresistance for Different Orientations of N-Type Cdas2 in the Variable-Range Hopping Regime. Mater. Sci. Eng., B 1994, 26, 19– 24,  DOI: 10.1016/0921-5107(94)90181-3
      [Crossref], [CAS], Google Scholar
      24
      Negative magnetoresistance for different orientations of n-type CdAs2 in the variable-range hopping regime
      Zdanowicz, E.; Wojciechowski, W.; Misiewicz, J.; Lisunov, K. G.
      Materials Science & Engineering, B: Solid-State Materials for Advanced Technology (1994), 26 (1), 19-24CODEN: MSBTEK; ISSN:0921-5107.
      The neg. magnetoresistance of Cd diarsenide in the variable-range hopping regime near the metal-nonmetal transition was analyzed by fitting the theor. model of Altshuler to the exptl. data. Expts. were performed for two different CdAs2 crystallog. orientations: [110] and [001]. There exists a region of magnetic fields and temps. in which the behavior of the neg. magnetoresistance corresponds completely to that predicted by Altshuler.
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    25. 25
      Oubraham, A.; Biskupski, G.; Zdanowicz, E. Negative Magnetoresistance of N-Type Compensated Cadmium Arsenide (CdSs2) in the Temperature Range 11 K-4.2 K. Solid State Commun. 1991, 77, 351– 354,  DOI: 10.1016/0038-1098(91)90749-L
      [Crossref], [CAS], Google Scholar
      25
      Negative magnetoresistance of n-type compensated cadmium diarsenide in the temperature range 11 K - 4.2 K
      Oubraham, A. A.; Biskupski, G.; Zdanowicz, E.
      Solid State Communications (1991), 77 (5), 351-4CODEN: SSCOA4; ISSN:0038-1098.
      The neg. magnetoresistance in compensated n-type CdAs2 with carrier d. n = 1.7 × 1017 cm-3 has been measured in the temp. range 4.2-11 K, in magnetic fields up to 1.5 T. Longitudinal and transverse magnetoresistance have similar behaviors. The exptl. data have been analyzed according to the V. Toyozawa (1962) model which suggests an addnl. scattering process of the carriers by localized magnetic moments. The transverse magnetoresistance which is treated here has the behavior of a system of paramagnetic spins. The variation of the neg. magnetoresistance vs. magnetic field and temp. is quite well approximated by a Langevin function with an effective magnetic moment μ* = n μB where μB is the μB and n = 8.
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    26. 26
      Gao, J.; Cupolillo, A.; Nappini, S.; Bondino, F.; Edla, R.; Fabio, V.; Sankar, R.; Zhang, Y. W.; Chiarello, G.; Politano, A. Surface Reconstruction, Oxidation Mechanism, and Stability of Cd3as2. Adv. Funct. Mater. 2019, 29, 1900965,  DOI: 10.1002/adfm.201900965
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    27. 27
      Červinka, L.; Hrubý, A. The Crystal Structure of CdSs2. Acta Crystallogr. B 1970, 26, 457– 458,  DOI: 10.1107/S0567740870002650
      [Crossref], [CAS], Google Scholar
      27
      Crystal structure of CdAs2
      Cervinka, Ladislav; Hruby, A.
      Acta Crystallographica, Section B: Structural Crystallography and Crystal Chemistry (1970), 26 (Pt. 4), 457-8CODEN: ACBCAR; ISSN:0567-7408.
      CdAs2 has a tetragonal structure with a = 7.96, c = 4.67 Å, c/a = 0.59; the measured d. is 5.8 and Z = 4. The space group is D104-I4122. Four Cd atoms are in the 4(b) position and 8 As atoms in the 8(f) position, with x = 0.06 ± 0.01.
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    28. 28
      Sales, B.; Jones, E.; Chakoumakos, B.; Fernandez-Baca, J.; Harmon, H.; Sharp, J.; Volckmann, E. Magnetic, Transport, and Structural Properties of Fe1–XIrxSi. Phys. Rev. B 1994, 50, 8207,  DOI: 10.1103/PhysRevB.50.8207
      [Crossref], [CAS], Google Scholar
      28
      Magnetic, transport, and structural properties of Fe1-xIrxSi
      Sales, B. C.; Jones, E. C.; Chakoumakos, B. C.; Fernandez-Baca, J. A.; Harmon, H. E.; Sharp, J. W.
      Physical Review B: Condensed Matter and Materials Physics (1994), 50 (12), 8207-13CODEN: PRBMDO; ISSN:0163-1829.
      Magnetic susceptibility, resistivity, Seebeck, Hall, and powder x-ray and neutron-diffraction measurements were used to characterize single crystals of FeSi and polycryst. samples of Fe1-xIrxSi for x <0.2. The Rietveld refinement of low-temp. powder neutron-diffraction data on FeSi showed no change in the space group and no structural anomalies from 4 to 300 k. Magnetic and transport data from 4 to 700 K are consistent with the characterization of FeSi as a narrow-gap semiconductor (Eg = 1200 K) with strong intrasite correlations for the states just below and above the gap. Fits to the magnetic susceptibility and resistivity data suggest that the magnetic (or direct) gap may be larger than the transport (indirect) gap. Electron mobilities in FeSi are very low (3-5 cm2/V s). The thermopower of FeSi has a large pos. peak (500 μV/K) at 50 K that is attributed to an unusually strong phonon-drag mechanism. Iridium acts as an electron donor in the Fe1-xIrxSi alloys. As the iridium doping level is increased, there is a rapid decrease in the low-temp. resistivity and a large neg. (-140 μV/K) phonon-drag contribution to the thermopower. For Peltier cooling applications, a max. value for ZT of 0.07 was found for a Fe0.95Ir0.05Si alloy at 100 K.
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    29. 29
      Pizzi, G.; Vitale, V.; Arita, R.; Blugel, S.; Freimuth, F.; Geranton, G.; Gibertini, M.; Gresch, D.; Johnson, C.; Koretsune, T.; Ibanez-Azpiroz, J.; Lee, H.; Lihm, J. M.; Marchand, D.; Marrazzo, A.; Mokrousov, Y.; Mustafa, J. I.; Nohara, Y.; Nomura, Y.; Paulatto, L.; Ponce, S.; Ponweiser, T.; Qiao, J.; Thole, F.; Tsirkin, S. S.; Wierzbowska, M.; Marzari, N.; Vanderbilt, D.; Souza, I.; Mostofi, A. A.; Yates, J. R. Wannier90 as a Community Code: New Features and Applications. J. Phys.: Condens. Matter 2020, 32, 165902,  DOI: 10.1088/1361-648X/ab51ff
      [Crossref], [PubMed], [CAS], Google Scholar
      29
      Wannier90 as a community code: new features and applications
      Pizzi, Giovanni; Vitale, Valerio; Arita, Ryotaro; Blugel, Stefan; Freimuth, Frank; Geranton, Guillaume; Gibertini, Marco; Gresch, Dominik; Johnson, Charles; Koretsune, Takashi; Ibanez-Azpiroz, Julen; Lee, Hyungjun; Lihm, Jae-Mo; Marchand, Daniel; Marrazzo, Antimo; Mokrousov, Yuriy; Mustafa, Jamal I.; Nohara, Yoshiro; Nomura, Yusuke; Paulatto, Lorenzo; Ponce, Samuel; Ponweiser, Thomas; Qiao, Junfeng; Thole, Florian; Tsirkin, Stepan S.; Wierzbowska, Malgorzata; Marzari, Nicola; Vanderbilt, David; Souza, Ivo; Mostofi, Arash A.; Yates, Jonathan R.
      Journal of Physics: Condensed Matter (2020), 32 (16), 165902CODEN: JCOMEL; ISSN:0953-8984. (IOP Publishing Ltd.)
      Wannier90 is an open-source computer program for calcg. maximally-localized Wannier functions (MLWFs) from a set of Bloch states. It is interfaced to many widely used electronic-structure codes thanks to its independence from the basis sets representing these Bloch states. In the past few years the development of Wannier90 has transitioned to a community-driven model; this has resulted in a no. of new developments that have been recently released in Wannier90 v3.0. In this article we describe these new functionalities, that include the implementation of new features for wannierisation and disentanglement (symmetry-adapted Wannier functions, selectively-localized Wannier functions, selected columns of the d. matrix) and the ability to calc. new properties (shift currents and Berry-curvature dipole, and a new interface to many-body perturbation theory); performance improvements, including parallelization of the core code; enhancements in functionality (support for spinor-valued Wannier functions, more accurate methods to interpolate quantities in the Brillouin zone); improved usability (improved plotting routines, integration with high-throughput automation frameworks), as well as the implementation of modern software engineering practices (unit testing, continuous integration, and automatic source-code documentation). These new features, capabilities, and code development model aim to further sustain and expand the community uptake and range of applicability, that nowadays spans complex and accurate dielec., electronic, magnetic, optical, topol. and transport properties of materials.
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    30. 30
      Wu, Q.; Zhang, S.; Song, H.-F.; Troyer, M.; Soluyanov, A. A. Wanniertools: An Open-Source Software Package for Novel Topological Materials. Comput. Phys. Commun. 2018, 224, 405– 416,  DOI: 10.1016/j.cpc.2017.09.033
      [Crossref], [CAS], Google Scholar
      30
      WannierTools : An open-source software package for novel topological materials
      Wu, QuanSheng; Zhang, ShengNan; Song, Hai-Feng; Troyer, Matthias; Soluyanov, Alexey A.
      Computer Physics Communications (2018), 224 (), 405-416CODEN: CPHCBZ; ISSN:0010-4655. (Elsevier B.V.)
      We present an open-source software package WannierTools, a tool for investigation of novel topol. materials. This code works in the tight-binding framework, which can be generated by another software package Wannier90 (Mostofi et al., 2008). It can help to classify the topol. phase of a given material by calcg. the Wilson loop, and can get the surface state spectrum, which is detected by angle resolved photoemission (ARPES) and in scanning tunneling microscopy (STM) expts. It also identifies positions of Weyl/Dirac points and nodal line structures, calcs. the Berry phase around a closed momentum loop and Berry curvature in a part of the Brillouin zone (BZ).Program title:WannierToolsProgram Files doi:http://dx.doi.org/10.17632/ygsmh4hyh6.1Licensing provisions: GNU General Public Licence 3.0Programming language: Fortran 90External routines/libraries used:BLAS (http://www/netlib.org/blas)LAPACK (http://www.netlib.org/lapack)Nature of problem: Identifying topol. classifications of cryst. systems including insulators, semimetals, metals, and studying the electronic properties of the related slab and ribbon systems.Soln. method: Tight-binding method is a good approxn. for solid systems. Based on that, Wilson loop is used for topol. phase classification. The iterative Green's function is used for obtaining the surface state spectrum.
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    31. 31
      He, W.-Y.; Xu, X. Y.; Law, K. T. Kramers Weyl Semimetals as Quantum Solenoids and Their Applications in Spin-Orbit Torque Devices. Commun. Phys. 2021, 4, 1– 8,  DOI: 10.1038/s42005-021-00564-w
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    32. 32
      Hafner, J. Ab-Initio Simulations of Materials Using Vasp: Density-Functional Theory and Beyond. J. Comput. Chem. 2008, 29, 2044– 2078,  DOI: 10.1002/jcc.21057
      [Crossref], [PubMed], [CAS], Google Scholar
      32
      Ab-initio simulations of materials using VASP: density-functional theory and beyond
      Hafner, Juergen
      Journal of Computational Chemistry (2008), 29 (13), 2044-2078CODEN: JCCHDD; ISSN:0192-8651. (John Wiley & Sons, Inc.)
      A review. During the past decade, computer simulations based on a quantum-mech. description of the interactions between electrons and between electrons and at. nuclei have developed an increasingly important impact on solid-state physics and chem. and on materials science-promoting not only a deeper understanding, but also the possibility to contribute significantly to materials design for future technologies. This development is based on two important columns: (i) The improved description of electronic many-body effects within d.-functional theory (DFT) and the upcoming post-DFT methods. (ii) The implementation of the new functionals and many-body techniques within highly efficient, stable, and versatile computer codes, which allow to exploit the potential of modern computer architectures. In this review, I discuss the implementation of various DFT functionals [local-d. approxn. (LDA), generalized gradient approxn. (GGA), meta-GGA, hybrid functional mixing DFT, and exact (Hartree-Fock) exchange] and post-DFT approaches [DFT + U for strong electronic correlations in narrow bands, many-body perturbation theory (GW) for quasiparticle spectra, dynamical correlation effects via the adiabatic-connection fluctuation-dissipation theorem (AC-FDT)] in the Vienna ab initio simulation package VASP. VASP is a plane-wave all-electron code using the projector-augmented wave method to describe the electron-core interaction. The code uses fast iterative techniques for the diagonalization of the DFT Hamiltonian and allows to perform total-energy calcns. and structural optimizations for systems with thousands of atoms and ab initio mol. dynamics simulations for ensembles with a few hundred atoms extending over several tens of ps. Applications in many different areas (structure and phase stability, mech. and dynamical properties, liqs., glasses and quasicrystals, magnetism and magnetic nanostructures, semiconductors and insulators, surfaces, interfaces and thin films, chem. reactions, and catalysis) are reviewed.
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    33. 33
      Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized Gradient Approximation Made Simple. Phys. Rev. Lett. 1996, 77, 3865– 3868,  DOI: 10.1103/PhysRevLett.77.3865
      [Crossref], [PubMed], [CAS], Google Scholar
      33
      Generalized gradient approximation made simple
      Perdew, John P.; Burke, Kieron; Ernzerhof, Matthias
      Physical Review Letters (1996), 77 (18), 3865-3868CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)
      Generalized gradient approxns. (GGA's) for the exchange-correlation energy improve upon the local spin d. (LSD) description of atoms, mols., and solids. We present a simple derivation of a simple GGA, in which all parameters (other than those in LSD) are fundamental consts. Only general features of the detailed construction underlying the Perdew-Wang 1991 (PW91) GGA are invoked. Improvements over PW91 include an accurate description of the linear response of the uniform electron gas, correct behavior under uniform scaling, and a smoother potential.
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    34. 34
      Kresse, G.; Joubert, D. From Ultrasoft Pseudopotentials to the Projector Augmented-Wave Method. Phys. Rev. B 1999, 59, 1758– 1775,  DOI: 10.1103/PhysRevB.59.1758
      [Crossref], [CAS], Google Scholar
      34
      From ultrasoft pseudopotentials to the projector augmented-wave method
      Kresse, G.; Joubert, D.
      Physical Review B: Condensed Matter and Materials Physics (1999), 59 (3), 1758-1775CODEN: PRBMDO; ISSN:0163-1829. (American Physical Society)
      The formal relationship between ultrasoft (US) Vanderbilt-type pseudopotentials and Blochl's projector augmented wave (PAW) method is derived. The total energy functional for US pseudopotentials can be obtained by linearization of two terms in a slightly modified PAW total energy functional. The Hamilton operator, the forces, and the stress tensor are derived for this modified PAW functional. A simple way to implement the PAW method in existing plane-wave codes supporting US pseudopotentials is pointed out. In addn., crit. tests are presented to compare the accuracy and efficiency of the PAW and the US pseudopotential method with relaxed-core all-electron methods. These tests include small mols. (H2, H2O, Li2, N2, F2, BF3, SiF4) and several bulk systems (diamond, Si, V, Li, Ca, CaF2, Fe, Co, Ni). Particular attention is paid to the bulk properties and magnetic energies of Fe, Co, and Ni.
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