Enhanced Berry Curvature Dipole and Persistent Spin Texture in the Bi(110) MonolayerClick to copy article linkArticle link copied!
- Kyung-Hwan Jin*Kyung-Hwan Jin*Email: [email protected]Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang 37673, Republic of KoreaMore by Kyung-Hwan Jin
- Eunseok OhEunseok OhCenter for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang 37673, Republic of KoreaDepartment of Physics, Pohang University of Science and Technology, Pohang 37673, Republic of KoreaMore by Eunseok Oh
- Roland StaniaRoland StaniaCenter for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang 37673, Republic of KoreaMore by Roland Stania
- Feng LiuFeng LiuDepartment of Materials Science and Engineering, University of Utah, Salt Lake City, Utah 84112, United StatesMore by Feng Liu
- Han Woong Yeom*Han Woong Yeom*Email: [email protected]Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang 37673, Republic of KoreaDepartment of Physics, Pohang University of Science and Technology, Pohang 37673, Republic of KoreaMore by Han Woong Yeom
Abstract
Nonvanishing Berry curvature dipole (BCD) and persistent spin texture (PST) are intriguing physical manifestations of electronic states in noncentrosymmetric 2D materials. The former induces a nonlinear Hall conductivity while the latter offers a coherent spin current. Based on density-functional-theory (DFT) calculations, we demonstrate the coexistence of both phenomena in a Bi(110) monolayer with a distorted phosphorene structure. Both effects are concurrently enhanced due to the strong spin–orbit coupling of Bi while the structural distortion creates internal in-plane ferroelectricity with inversion asymmetry. We further succeed in fabricating a Bi(110) monolayer in the desired phosphorene structure on the NbSe2 substrate. Detailed atomic and electronic structures of the Bi(110)/NbSe2 heterostructure are characterized by scanning tunneling microscopy/spectroscopy and angle-resolved-photoemission spectroscopy. These results are consistent with DFT calculations which indicate the large BCD and PST are retained. Our results suggest the Bi(110)/NbSe2 heterostructure as a promising platform to exploit nonlinear Hall and coherent spin transport properties together.
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Results and Discussion
Atomic and Electronic Structure of the Bi(110) Monolayer

symmetry | (x, y, z) form | operation |
---|---|---|
identity | (x, y, z) | {1|0} |
mirror | x, −y, z | {M010|0} ≡ M010 |
glide plane | –x, y + 1/2, z + 1/2 | {M100|0, 1/2, 1/2} |
rotation | –x, −y + 1/2, z + 1/2 | {2001|0, 1/2, 1/2} |
Figure 1
Figure 1. Atomic structure and electronic structure of the Bi(110) monolayer. (a) Top and side views of atomic structures of flat and puckered Bi(110) monolayer. (b, c) Calculated band structure of flat and puckered Bi(110) monolayer, respectively. The inset in c shows the BZ. The red (blue) arrow indicates the crossing point (SOC gap) along the X–M path. (d) 3D band plot of the puckered Bi(110) near the Γ point as indicated by the red line in the inset of (c). (e) Calculated band structure of the puckered Bi(110) monolayer under different out-of-plane electric fields, Ez = 0.0, 0.05, and 0.1 eV/Å. (f) Enlarged band structure as indicated by the red box in (e). (g) 3D band plot near the Γ point as indicated by the black box in (e).
BCD and Nonlinear Anomalous Hall Effect

Figure 2
Figure 2. Berry curvature properties of the Bi(110) monolayer. The calculated Berry curvature Ωz(k) of the puckered Bi(110) monolayer in the first Brillouin zone (BZ) at different Fermi energies; (a) E = 0 eV (all valence bands occupied), (b) E = −0.34 eV, and (c) E = −0.45 eV (parts of the valence bands are empty). The black arrow shows the direction of BCD vector Dy. (d) BC that is calculated along the −Y–G–Y line in under varying the out-of-plane electric fields (Ez). (e) Calculated BCD (Dy) of the puckered Bi(110) monolayer with varying Ez. The Fermi level (E = 0 eV) is based on the middle of the band gap of the Bi(110) monolayer.
PST in the Ferroelectric Bi(110) Monolayer

Figure 3
Figure 3. Spin texture of the Bi(110) monolayer. (a) Spin resolved band structure of the puckered Bi(110) monolayer along the Γ–Y direction. (b) Spin texture measured at the constant-energy cut-off E = 0.37 eV as indicated by dashed line in (a). The in-plane polarization induces the unidirectional (z-direction) spin polarized spin texture. (c, d) Spin texture measured for the out-of-plane electric field Ez = 0.05 eV/Å and Ez = 0.1 eV/Å at the constant-energy cut-off E = 0.37 eV, respectively.

Bi(110) Films Grown on the NbSe2 Substrate
Figure 4
Figure 4. Bi/NbSe2 heterostructure model and the corresponding STM images. (a) Side and top views of the Bi/NbSe2 structural model consisting of a 6 × 3 Bi(110) monolayer on a 5√3 × 4 NbSe2 substrate. (b) STM morphology of Bi(110) films grown on a NbSe2 substrate (constant-current mode with Vbias = +0.5 V, lt = 100 pA, and 4.3 K). A narrow-area STM image of the Bi(110) 1L surface at (c) Vbias= +0.5 V, lt = 5000 pA, and 4.43 K and (d) Vbias= −0.5 V, lt = 5000 pA, and 4.43 K, respectively. (e) Atomically resolved STM image of the Bi(110) monolayer surface (left panel) for Vbias = +0.5 V and simulated STM image by integrating the orbitals from the Fermi level to 0.5 eV (right panel). (f) Atomically resolved STM image of the Bi(110) surface (left panel) for Vbias = −0.5 V and simulated STM image by integrating the orbitals from the Fermi level to −0.5 eV (right panel). (g) Experimental and simulated line profiles taken along the arrow marked in (e) and (f). (h) dI/dV/(I/V) spectra at fixed positions and projected DOS (PDOS) of the Bi atoms indicated by blue and red points in (a). The normalized dI/dV curves are taken from the bright and dark areas of the Moiré pattern as indicated by the blue and red points in the inset image, respectively. (i) Unfolded band structure and the corresponding spin-resolved band structure of the heterostructure Bi/NbSe2 model into the Brillouin zone of the Bi(110) monolayer unit cell for the equilibrium (d = 0 Å) and increased (d = 3 Å) bonding distance, respectively.
Figure 5
Figure 5. Reshaped band structure of the Bi/NbSe2 heterostructure. (a) Photoemission intensity and calculated band structure for pristine NbSe2, respectively. Green dashed lines overlaid on top of the ARPES map are the calculated band dispersions. (b) Photoemission intensity and unfolded band structure into primitive NbSe2 BZ for heterostructure Bi(110)/NbSe2, respectively.
Conclusions
Supporting Information
The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.nanolett.1c02811.
Computational and experimental methods, electron/hole doping dependent stability, the SOC splitting of the valence and conduction bands, the distribution of the Berry curvature gradient, Berry curvature with the opposite polarization, band structures of the Bi(110) monolayer under an out-of-plane electric field, the conventional Rashba and out-of-plane Rashba model, large-scale topography, surface characterization via XPD, interface effect on band structures, charge density difference of the Bi/NbSe2 interface, origin of the linear dispersion, and the BCD for Bi/NbSe2 heterosystem (PDF)
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Acknowledgments
This work was supported by the Institute for Basic Science (Grant No. IBS-R014-D1). K.-H.J. is supported by the Institute for Basic Science (Grant No. IBS-R014-Y1). F.L. acknowledges the support from US-DOE (Grant No. DE-FG02-04ER46148).
References
This article references 38 other publications.
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- 2Xu, S.-Y.; Ma, Q.; Shen, H.; Fatemi, V.; Wu, S.; Chang, T.-R.; Chang, G.; Valdivia, A. M. M.; Chan, C.-K.; Gibson, Q. D.; Zhou, J.; Liu, Z.; Watanabe, K.; Taniguchi, T.; Lin, H.; Cava, R. J.; Fu, L.; Gedik, N.; Jarillo-Herrero, P. Electrically switchable Berry curvature dipole in the monolayer topological insulator WTe2. Nat. Phys. 2018, 14 (9), 900– 906, DOI: 10.1038/s41567-018-0189-6Google Scholar2https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXht1Kltr3K&md5=19cd6eed84f5e743c96b95c5726363b6Electrically switchable Berry curvature dipole in the monolayer topological insulator WTe2Xu, Su-Yang; Ma, Qiong; Shen, Huitao; Fatemi, Valla; Wu, Sanfeng; Chang, Tay-Rong; Chang, Guoqing; Valdivia, Andres M. Mier; Chan, Ching-Kit; Gibson, Quinn D.; Zhou, Jiadong; Liu, Zheng; Watanabe, Kenji; Taniguchi, Takashi; Lin, Hsin; Cava, Robert J.; Fu, Liang; Gedik, Nuh; Jarillo-Herrero, PabloNature Physics (2018), 14 (9), 900-906CODEN: NPAHAX; ISSN:1745-2473. (Nature Research)Recent exptl. evidence for the quantum spin Hall (QSH) state in monolayer WTe2 has linked the fields of two-dimensional materials and topol. physics1-7. This two-dimensional topol. crystal also displays unconventional spin-torque8 and gate-tunable supercond.7. Whereas the realization of the QSH has demonstrated the nontrivial topol. of the electron wavefunctions of monolayer WTe2, the geometrical properties of the wavefunction, such as the Berry curvature9, remain unstudied. Here we utilize mid-IR optoelectronic microscopy to investigate the Berry curvature in monolayer WTe2. By optically exciting electrons across the inverted QSH gap, we observe an in-plane circular photogalvanic current even under normal incidence. The application of an out-of-plane displacement field allows further control of the direction and magnitude of the photocurrent. The obsd. photocurrent reveals a Berry curvature dipole that arises from the nontrivial wavefunctions near the inverted gap edge. The Berry curvature dipole and strong elec. field effect are enabled by the inverted band structure and tilted crystal lattice of monolayer WTe2. Such an elec. switchable Berry curvature dipole may facilitate the observation of a wide range of quantum geometrical phenomena such as the quantum nonlinear Hall10,11, orbital-Edelstein12 and chiral polaritonic effects13,14.
- 3Ma, Q.; Xu, S.-Y.; Shen, H.; MacNeill, D.; Fatemi, V.; Chang, T.-R.; Mier Valdivia, A. M.; Wu, S.; Du, Z.; Hsu, C.-H.; Fang, S.; Gibson, Q. D.; Watanabe, K.; Taniguchi, T.; Cava, R. J.; Kaxiras, E.; Lu, H.-Z.; Lin, H.; Fu, L.; Gedik, N.; Jarillo-Herrero, P. Observation of the nonlinear Hall effect under time-reversal-symmetric conditions. Nature 2019, 565 (7739), 337– 342, DOI: 10.1038/s41586-018-0807-6Google Scholar3https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXisFCitbvF&md5=de981565b3691a251009e42fc4f4dcd8Observation of nonlinear Hall effect under time-reversal-symmetric conditionsMa, Qiong; Xu, Su-Yang; Shen, Huitao; MacNeill, David; Fatemi, Valla; Chang, Tay-Rong; Mier Valdivia, Andres M.; Wu, Sanfeng; Du, Zongzheng; Hsu, Chuang-Han; Fang, Shiang; Gibson, Quinn D.; Watanabe, Kenji; Taniguchi, Takashi; Cava, Robert J.; Kaxiras, Efthimios; Lu, Hai-Zhou; Lin, Hsin; Fu, Liang; Gedik, Nuh; Jarillo-Herrero, PabloNature (London, United Kingdom) (2019), 565 (7739), 337-342CODEN: NATUAS; ISSN:0028-0836. (Nature Research)The elec. Hall effect is the prodn., upon the application of an elec. field, of a transverse voltage under an out-of-plane magnetic field. Studies of the Hall effect have led to important breakthroughs, including the discoveries of Berry curvature and topol. Chern invariants1,2. The internal magnetization of magnets means that the elec. Hall effect can occur in the absence of an external magnetic field2; this 'anomalous' Hall effect is important for the study of quantum magnets2-7. The elec. Hall effect has rarely been studied in non-magnetic materials without external magnetic fields, owing to the constraint of time-reversal symmetry. However, only in the linear response regime-when the Hall voltage is linearly proportional to the external elec. field-does the Hall effect identically vanish as a result of time-reversal symmetry; the Hall effect in the nonlinear response regime is not subject to such symmetry constraints8-10. Here we report observations of the nonlinear Hall effect10 in elec. transport in bilayers of the non-magnetic quantum material WTe2 under time-reversal-sym. conditions. We show that an elec. current in bilayer WTe2 leads to a nonlinear Hall voltage in the absence of a magnetic field. The properties of this nonlinear Hall effect are distinct from those of the anomalous Hall effect in metals: the nonlinear Hall effect results in a quadratic, rather than linear, current-voltage characteristic and, in contrast to the anomalous Hall effect, the nonlinear Hall effect results in a much larger transverse than longitudinal voltage response, leading to a nonlinear Hall angle (the angle between the total voltage response and the applied elec. field) of nearly 90 degrees. We further show that the nonlinear Hall effect provides a direct measure of the dipole moment10 of the Berry curvature, which arises from layer-polarized Dirac fermions in bilayer WTe2. Our results demonstrate a new type of Hall effect and provide a way of detecting Berry curvature in non-magnetic quantum materials.
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- 6Tao, L. L.; Tsymbal, E. Y. Persistent spin texture enforced by symmetry. Nat. Commun. 2018, 9 (1), 2763, DOI: 10.1038/s41467-018-05137-0Google Scholar6https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADC%252BB3c%252Fpt1WjsA%253D%253D&md5=76809f9af9a74bd82fa1459c04d59083Persistent spin texture enforced by symmetryTao L L; Tsymbal Evgeny YNature communications (2018), 9 (1), 2763 ISSN:.Persistent spin texture (PST) is the property of some materials to maintain a uniform spin configuration in the momentum space. This property has been predicted to support an extraordinarily long spin lifetime of carriers promising for spintronics applications. Here, we predict that there exists a class of noncentrosymmetric bulk materials, where the PST is enforced by the nonsymmorphic space group symmetry of the crystal. Around certain high symmetry points in the Brillouin zone, the sublattice degrees of freedom impose a constraint on the effective spin-orbit field, which orientation remains independent of the momentum and thus maintains the PST. We illustrate this behavior using density-functional theory calculations for a handful of promising candidates accessible experimentally. Among them is the ferroelectric oxide BiInO3-a wide band gap semiconductor which sustains a PST around the conduction band minimum. Our results broaden the range of materials that can be employed in spintronics.
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- 11Avsar, A.; Ochoa, H.; Guinea, F.; Özyilmaz, B.; van Wees, B. J.; Vera-Marun, I. J. Colloquium: Spintronics in graphene and other two-dimensional materials. Rev. Mod. Phys. 2020, 92 (2), 021003, DOI: 10.1103/RevModPhys.92.021003Google Scholar11https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXitFWnsb3I&md5=a30d987f298212590a1d11c91714f4aaColloquium: Spintronics in graphene and other two-dimensional materialsAvsar, A.; Ochoa, H.; Guinea, F.; Ozyilmaz, B.; van Wees, B. J.; Vera-Marun, I. J.Reviews of Modern Physics (2020), 92 (2), 021003CODEN: RMPHAT; ISSN:1539-0756. (American Physical Society)A review. After the first unequivocal demonstration of spin transport in graphene [Tombros et al., Nature (London) 448, 571-574 (2007)], surprisingly at room temp., it was quickly realized that this novel material was relevant for both fundamental spintronics and future applications. In the decade since, exciting results have made the field of graphene spintronics blossom, and a second generation of studies has extended to new two-dimensional (2D) compds. This Colloquium reviews recent theor. and exptl. advances on electronic spin transport in graphene and related 2D materials, focusing on emergent phenomena in van der Waals heterostructures and the new perspectives provided by them. These phenomena include proximity-enabled spin-orbit effects, the coupling of electronic spin to light, elec. tunability, and 2D magnetism.
- 12You, J.-S.; Fang, S.; Xu, S.-Y.; Kaxiras, E.; Low, T. Berry curvature dipole current in the transition metal dichalcogenides family. Phys. Rev. B: Condens. Matter Mater. Phys. 2018, 98 (12), 121109, DOI: 10.1103/PhysRevB.98.121109Google ScholarThere is no corresponding record for this reference.
- 13Du, Z. Z.; Wang, C. M.; Lu, H.-Z.; Xie, X. C. Band Signatures for Strong Nonlinear Hall Effect in Bilayer WTe2. Phys. Rev. Lett. 2018, 121 (26), 266601, DOI: 10.1103/PhysRevLett.121.266601Google Scholar13https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXlslCqtLo%253D&md5=1400ee25ef1075104a72f7b69403cbdaBand signatures for strong nonlinear hall effect in bilayer WTe2Du, Z. Z.; Wang, C. M.; Lu, Hai-Zhou; Xie, X. C.Physical Review Letters (2018), 121 (26), 266601/1-266601/6CODEN: PRLTAO; ISSN:1079-7114. (American Physical Society)Unconventional responses upon breaking discrete or crystal symmetries open avenues for exploring emergent phys. systems and materials. By breaking inversion symmetry, a nonlinear Hall signal can be obsd., even in the presence of time-reversal symmetry, quite different from the conventional Hall effects. Low-symmetry two-dimensional materials are promising candidates for the nonlinear Hall effect, but it is less known when a strong nonlinear Hall signal can be measured, in particular, its connections with the band-structure properties. By using model anal., we find prominent nonlinear Hall signals near tilted band anticrossings and band inversions. These band signatures can be used to explain the strong nonlinear Hall effect in the recent expts. on two-dimensional WTe2. This Letter will be instructive not only for analyzing the transport signatures of the nonlinear Hall effect but also for exploring unconventional responses in emergent materials.
- 14Kim, J.; Kim, K.-W.; Shin, D.; Lee, S.-H.; Sinova, J.; Park, N.; Jin, H. Prediction of ferroelectricity-driven Berry curvature enabling charge- and spin-controllable photocurrent in tin telluride monolayers. Nat. Commun. 2019, 10 (1), 3965, DOI: 10.1038/s41467-019-11964-6Google Scholar14https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADC%252BB3MrkvVChtA%253D%253D&md5=c77bc43aab98e557dd8600eb670b05ddPrediction of ferroelectricity-driven Berry curvature enabling charge- and spin-controllable photocurrent in tin telluride monolayersKim Jeongwoo; Shin Dongbin; Park Noejung; Jin Hosub; Kim Jeongwoo; Kim Kyoung-Whan; Kim Kyoung-Whan; Sinova Jairo; Lee Sang-Hoon; Sinova JairoNature communications (2019), 10 (1), 3965 ISSN:.In symmetry-broken crystalline solids, pole structures of Berry curvature (BC) can emerge, and they have been utilized as a versatile tool for controlling transport properties. For example, the monopole component of the BC is induced by the time-reversal symmetry breaking, and the BC dipole arises from a lack of inversion symmetry, leading to the anomalous Hall and nonlinear Hall effects, respectively. Based on first-principles calculations, we show that the ferroelectricity in a tin telluride monolayer produces a unique BC distribution, which offers charge- and spin-controllable photocurrents. Even with the sizable band gap, the ferroelectrically driven BC dipole is comparable to those of small-gap topological materials. By manipulating the photon handedness and the ferroelectric polarization, charge and spin circular photogalvanic currents are generated in a controllable manner. The ferroelectricity in group-IV monochalcogenide monolayers can be a useful tool to control the BC dipole and the nonlinear optoelectronic responses.
- 15Absor, M. A. U.; Ishii, F. Intrinsic persistent spin helix state in two-dimensional group-IV monochalcogenide MX monolayers (M = Sn or Ge and X = S, Se, or Te). Phys. Rev. B: Condens. Matter Mater. Phys. 2019, 100 (11), 115104, DOI: 10.1103/PhysRevB.100.115104Google ScholarThere is no corresponding record for this reference.
- 16Sławińska, J.; Cerasoli, F. T.; Gopal, P.; Costa, M.; Curtarolo, S.; Buongiorno Nardelli, M. Ultrathin SnTe films as a route towards all-in-one spintronics devices. 2D Mater. 2020, 7 (2), 025026, DOI: 10.1088/2053-1583/ab6f7aGoogle Scholar16https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXitFCiurfF&md5=82a2a6f59ba19ccbf403f12536e4e8eeUltrathin SnTe films as a route towards all-in-one spintronics devicesSlawinska, Jagoda; Cerasoli, Frank T.; Gopal, Priya; Costa, Marcio; Curtarolo, Stefano; Nardelli, Marco Buongiorno2D Materials (2020), 7 (2), 025026CODEN: DMATB7; ISSN:2053-1583. (IOP Publishing Ltd.)Spin transistors based on a semiconducting channel attached to ferromagnetic electrodes suffer from fast spin decay and extremely low spin injection/detection efficiencies. Here, we propose an alternative all-in-one spin device whose operation principle relies on elec. manipulation of the spin lifetime in two-dimensional (2D) SnTe, in which the sizable spin Hall effect eliminates the need for using ferromagnets. In particular, we explore the persistent spin texture (PST) intrinsically present in the ferroelec. phase which protects the spin from decoherence and supports extraordinarily long spin lifetime. Our first-principles calcns. followed by symmetry arguments revealed that such a spin wave mode can be externally detuned by perpendicular elec. field, leading to spin randomization and decrease in spin lifetime. We further extend our anal. to ultrathin SnTe films and confirm the emergence of PST as well as a moderate enhancement of intrinsic spin Hall cond. The recent room-temp. observation of the ferroelec. phase in 2D-SnTe suggests that novel all-elec. spintronics devices are within reach.
- 17Bian, G.; Wang, X.; Miller, T.; Chiang, T. C.; Kowalczyk, P. J.; Mahapatra, O.; Brown, S. A. First-principles and spectroscopic studies of Bi(110) films: Thickness-dependent Dirac modes and property oscillations. Phys. Rev. B: Condens. Matter Mater. Phys. 2014, 90 (19), 195409, DOI: 10.1103/PhysRevB.90.195409Google Scholar17https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhsVKmtbg%253D&md5=3d171b7880915307928baf756f8ea8e9First-principles and spectroscopic studies of Bi(110) films: thickness-dependent Dirac modes and property oscillationsBian, G.; Wang, X.; Miller, T.; Chiang, T.-C.; Kowalczyk, P. J.; Mahapatra, O.; Brown, S. A.Physical Review B: Condensed Matter and Materials Physics (2014), 90 (19), 195409/1-195409/7, 7 pp.CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)The electronic structure of Bi(110) thin films as a function of film thickness is investigated by first-principles calcns., angle-resolved photoemission spectroscopy, and scanning tunneling microscopy. Energy minimization in the calcn. reveals significant at. relaxation and rebonding at the surface. The calcd. surface energy for the relaxed structures indicates that films consisting of odd nos. of at. layers are inherently unstable and tend to bifurcate into film domains consisting of neighboring even nos. of at. layers. This theor. trend agrees with exptl. observations. The results can be explained by the presence of unsatd. pz dangling bonds on the surfaces of films of odd-numbered at. layers only. These pz dangling bonds form a Dirac-cone feature near the Fermi level at the ‾M point as a consequence of the interplay of mirror symmetry and spin-orbit coupling. Films consisting of even nos. of at. layers exhibit a band gap at ‾M instead.
- 18Lu, Y.; Zhou, D.; Chang, G.; Guan, S.; Chen, W.; Jiang, Y.; Jiang, J.; Wang, X.-s.; Yang, S. A.; Feng, Y. P.; Kawazoe, Y.; Lin, H. Multiple unpinned Dirac points in group-Va single-layers with phosphorene structure. npj Comput. Mater. 2016, 2 (1), 16011, DOI: 10.1038/npjcompumats.2016.11Google ScholarThere is no corresponding record for this reference.
- 19Pumera, M.; Sofer, Z. 2D Monoelemental Arsenene, Antimonene, and Bismuthene: Beyond Black Phosphorus. Adv. Mater. 2017, 29 (21), 1605299, DOI: 10.1002/adma.201605299Google ScholarThere is no corresponding record for this reference.
- 20Jin, K.-H.; Huang, H.; Wang, Z.; Liu, F. A 2D nonsymmorphic Dirac semimetal in a chemically modified group-VA monolayer with a black phosphorene structure. Nanoscale 2019, 11 (15), 7256– 7262, DOI: 10.1039/C9NR00906JGoogle Scholar20https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXltFGntLY%253D&md5=26d94c1868514770fd3d5640d0c297afA 2D nonsymmorphic Dirac semimetal in a chemically modified group-VA monolayer with a black phosphorene structureJin, Kyung-Hwan; Huang, Huaqing; Wang, Zhengfei; Liu, FengNanoscale (2019), 11 (15), 7256-7262CODEN: NANOHL; ISSN:2040-3372. (Royal Society of Chemistry)A symmetry-protected 2D Dirac semimetal has attracted intense interest for its intriguing material properties. Here, we report a 2D nonsymmorphic Dirac semimetal state in a chem. modified group-VA 2D puckered structure. Based on first-principles calcns., we demonstrate the existence of 2D Dirac fermions in a one-side modified phosphorene structure in two different types: one with a Dirac nodal line (DNL) structure for light elements with negligible spin-orbit coupling (SOC) and the other having an hourglass band protected by a nonsymmorphic symmetry for heavy elements with strong SOC. In the absence of SOC, the DNL exhibits an anisotropic behavior and unique electronic properties, such as const. d. of states. The Dirac node is protected from gap opening by the nonsymmorphic space group symmetry. In the presence of SOC, the DNL states split and form an hourglass-shaped dispersion due to the broken inversion symmetry and the Rashba SOC interaction. Moreover, around certain high symmetry points in the Brillouin zone, the spin orientation is enforced to be along a specific direction. We construct an effective tight-binding model to characterize the 2D nonsymmorphic Dirac states. Our result provides a promising material platform for exploring the intriguing properties of essential nodal-line and nodal-point fermions in 2D systems.
- 21Peng, L.; Qiao, J.; Xian, J.-J.; Pan, Y.; Ji, W.; Zhang, W.; Fu, Y.-S. Unusual Electronic States and Superconducting Proximity Effect of Bi Films Modulated by a NbSe2 Substrate. ACS Nano 2019, 13 (2), 1885– 1892, DOI: 10.1021/acsnano.8b08051Google Scholar21https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhsFajtLs%253D&md5=ad52c19437e320c7b22a220f6fef602eUnusual Electronic States and Superconducting Proximity Effect of Bi Films Modulated by a NbSe2 SubstratePeng, Lang; Qiao, Jingsi; Xian, Jing-Jing; Pan, Yuhao; Ji, Wei; Zhang, Wenhao; Fu, Ying-ShuangACS Nano (2019), 13 (2), 1885-1892CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)Heterostructures of two-dimensional layered materials can be functionalized with exotic phenomena that are unpresented with each constituting component. The interface effect plays a key role in detg. the electronic properties of the heterostructure, whose characterization requires a correlation with the morphol. with at.-scale precision. Here, we report an investigation on the electronic properties of few-layer Bi(110) films mediated by a NbSe2 substrate. By utilizing scanning tunneling microscopy and spectroscopy, we show a significant variation of the d. of states at different Bi film thicknesses, resulting in an unusual superconducting proximity effect that deviates from the conventional monotonous decay behavior. Moreover, the electronic states of the Bi films are also prominently modulated by the Moir´e pattern spatially. With first-principles calcns., we illuminate these findings as the results of covalent-like quasi-bonds formed at the Bi/NbSe2 interface, which profoundly alter the charge distributions in the Bi films. Our study indicates a viable way of modulating the electronic properties of ultrathin films by quasi-covalent interfacial couplings beyond conventional van der Waals interactions.
- 22Dong, X.; Li, Y.; Li, J.; Peng, X.; Qiao, L.; Chen, D.; Yang, H.; Xiong, X.; Wang, Q.; Li, X.; Duan, J.; Han, J.; Xiao, W. Epitaxial Growth and Structural Properties of Bi(110) Thin Films on TiSe2 Substrates. J. Phys. Chem. C 2019, 123 (22), 13637– 13641, DOI: 10.1021/acs.jpcc.9b01923Google Scholar22https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXptlelsLs%253D&md5=221079a78aceb8c02eb9afd82caad6bfEpitaxial Growth and Structural Properties of Bi(110) Thin Films on TiSe2 SubstratesDong, Xu; Li, Yongkai; Li, Ji; Peng, Xianglin; Qiao, Lu; Chen, Dongyun; Yang, Huixia; Xiong, Xiaolu; Wang, Qinsheng; Li, Xiang; Duan, Junxi; Han, Junfeng; Xiao, WendeJournal of Physical Chemistry C (2019), 123 (22), 13637-13641CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)We report the growth and structural properties of Bi thin films on TiSe2 substrates by using a low-temp. scanning tunneling microscope. Extended Bi(110) thin films are formed on the TiSe2 substrates and adopt a distorted black-phosphorus structure at room temp. (RT). The diagonal of the Bi(110) rectangular unit cell is parallel to the close-packed direction of the top-layer Se atoms of the TiSe2 substrates, resulting in the formation of a stripe-shaped commensurate moir´e pattern with a periodicity of ∼38.5 Å at RT. Meanwhile, the charge d. wave phase transition of the TiSe2 substrate and the different coeffs. of thermal expansion of Bi(110) and TiSe2 lead to the formation of a quasi-hexagonal incommensurate moir´e pattern with a periodicity of 14.5 Å at 77 K. In particular, the combination of domains with twisting angles of 30° or 60° results in the formation of various domain boundaries. Our work is very helpful for understanding and tuning the structural and electronic properties of epitaxial Bi(110) thin films.
- 23Ju, S.; Wu, M.; Yang, H.; Wang, N.; Zhang, Y.; Wu, P.; Wang, P.; Zhang, B.; Mu, K.; Li, Y.; Guan, D.; Qian, D.; Lu, F.; Liu, D.; Wang, W.-H.; Chen, X.; Sun, Z. Band Structures of Ultrathin Bi(110) Films on Black Phosphorus Substrates Using Angle-Resolved Photoemission Spectroscopy. Chin. Phys. Lett. 2018, 35 (7), 077102, DOI: 10.1088/0256-307X/35/7/077102Google Scholar23https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXlsVGqtL0%253D&md5=c9386d7364f8c7b86305a996e37312eaBand structures of ultrathin Bi(110) films on black phosphorus substrates using angle-resolved photoemission spectroscopyJu, Sailong; Wu, Maokun; Yang, Hao; Wang, Naizhou; Zhang, Yingying; Wu, Peng; Wang, Pengdong; Zhang, Bo; Mu, Kejun; Li, Yaoyi; Guan, Dandan; Qian, Dong; Lu, Feng; Liu, Dayong; Wang, Wei-Hua; Chen, Xianhui; Sun, ZheChinese Physics Letters (2018), 35 (7), 077102/1-077102/5CODEN: CPLEEU; ISSN:1741-3540. (IOP Publishing Ltd.)The band structures of two-monolayer Bi(110) films on black phosphorus substrates are studied using angleresolved photoemission spectroscopy. Within the band gap of bulk black phosphorus, the electronic states near the Fermi level are dominated by the Bi(110) film. The band dispersions revealed by our data suggest that the orientation of the Bi(110) film is aligned with the black phosphorus substrate. The electronic structures of the Bi(110) film strongly deviate from the band calcns. of the free-standing Bi(110) film, suggesting that the substrate can significantly affect the electronic states in the Bi(110) film. Our data show that there are no non-trivial electronic states in Bi(110) films grown on black phosphorus substrates.
- 24Lu, Y.; Xu, W.; Zeng, M.; Yao, G.; Shen, L.; Yang, M.; Luo, Z.; Pan, F.; Wu, K.; Das, T.; He, P.; Jiang, J.; Martin, J.; Feng, Y. P.; Lin, H.; Wang, X.-s. Topological Properties Determined by Atomic Buckling in Self-Assembled Ultrathin Bi(110). Nano Lett. 2015, 15 (1), 80– 87, DOI: 10.1021/nl502997vGoogle Scholar24https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXitFaqsLfP&md5=c7c2e7bc71184fb0202bad73254c3fd8Topological Properties Determined by Atomic Buckling in Self-Assembled Ultrathin Bi(110)Lu, Yunhao; Xu, Wentao; Zeng, Mingang; Yao, Guanggeng; Shen, Lei; Yang, Ming; Luo, Ziyu; Pan, Feng; Wu, Ke; Das, Tanmoy; He, Pimo; Jiang, Jianzhong; Martin, Jens; Feng, Yuan Ping; Lin, Hsin; Wang, Xue-senNano Letters (2015), 15 (1), 80-87CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)Topol. insulators (TIs) are a new type of electronic materials in which the nontrivial insulating bulk band topol. governs conducting boundary states with embedded spin-momentum locking. Such edge states are more robust in a two-dimensional (2D) TI against scattering by nonmagnetic impurities than in its three-dimensional (3D) variant, because in 2D the two helical edge states are protected from the only possible backscattering. This makes the 2D TI family a better candidate for coherent spin transport and related applications. While several 3D TIs are already synthesized exptl., phys. realization of 2D TI is so far limited to hybrid quantum wells with a tiny bandgap that does not survive temps. above 10 K. Here, combining first-principles calcns. and scanning tunneling microscopy/spectroscopy (STM/STS) exptl. studies, we report nontrivial 2D TI phases in 2-monolayer (2-ML) and 4-ML Bi(110) films with large and tunable bandgaps detd. by at. buckling of Bi(110) films. The gapless edge states are exptl. detected within the insulating bulk gap at 77 K. The band topol. of ultrathin Bi(110) films is sensitive to at. buckling. Such buckling is sensitive to charge doping and could be controlled by choosing different substrates on which Bi(110) films are grown.
- 25Kokubo, I.; Yoshiike, Y.; Nakatsuji, K.; Hirayama, H. Ultrathin Bi(110) films on Si(111)√3×√3-B substrates. Phys. Rev. B: Condens. Matter Mater. Phys. 2015, 91 (7), 075429, DOI: 10.1103/PhysRevB.91.075429Google Scholar25https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXptlClt7g%253D&md5=0c5a82b472d10904bc05066d3f5f9152Ultrathin Bi(110) films on Si(111)√ ×3 √3-B substratesKokubo, Ikuya; Yoshiike, Yusaku; Nakatsuji, Kan; Hirayama, HiroyukiPhysical Review B: Condensed Matter and Materials Physics (2015), 91 (7), 075429/1-075429/7CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)We studied the structure of ultrathin Bi(110) films on Si(111)√3 × √3-B substrates using scanning tunneling microscopy. Atomically flat Bi islands were nucleated on the substrates at room temp. The edges of these islands were parallel to the short side of the Bi(110) rectangular unit cell. The islands extended along six specific orientations because the rectangular Bi(110) and rhombus √3 × √3 unit cells were commensurate at the interface. Bi(110) domains along different orientations coexisted and formed various domain boundary structures on the wide terraces of the islands. In particular, the domains along ±87° from the {‾110} direction were connected perfectly on an at. scale by changing the direction of the p-like bond of the in-plane zigzag chains locally at the straight domain boundary. No exclusive preference for the black phosphorus structure was obsd. for the Bi(110) ultrathin films, in contrast to the islands grown on the Si(111)7 × 7 substrate.
- 26Zhang, Y.; van den Brink, J.; Felser, C.; Yan, B. H. Electrically tuneable nonlinear anomalous Hall effect in two-dimensional transition-metal dichalcogenides WTe2 and MoTe2. 2D Mater. 2018, 5 (4), 044001, DOI: 10.1088/2053-1583/aad1aeGoogle Scholar26https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhvFeiu7nM&md5=d0dfb6c1eaffd3aec1d7a99b9ce543eaElectrically tuneable nonlinear anomalous Hall effect in two-dimensional transition-metal dichalcogenides WTe2 and MoTe2Zhang, Yang; van den Brink, Jeroen; Felser, Claudia; Yan, Binghai2D Materials (2018), 5 (4), 044001CODEN: DMATB7; ISSN:2053-1583. (IOP Publishing Ltd.)We studied the nonlinear elec. response in WTe2 and MoTe2 monolayers. When the inversion symmetry is breaking but the the time-reversal symmetry is preserved, a second-order Hall effect called the nonlinear anomalous Hall effect (NLAHE) emerges owing to the nonzero Berry curvature on the nonequil. Fermi surface. We reveal a strong NLAHE with a Hall-voltage that is quadratic with respect to the longitudinal current. The optimal current direction is normal to the mirror plane in these two-dimensional (2D) materials. The NLAHE can be sensitively tuned by an out-of-plane elec. field, which induces a transition from a topol. insulator to a normal insulator. Crossing the crit. transition point, the magnitude of the NLAHE increases, and its sign is reversed. Our work paves the way to discover exotic nonlinear phenomena in inversion-symmetry-breaking 2D materials.
- 27Xiao, C.; Wang, F.; Yang, S. A.; Lu, Y.; Feng, Y.; Zhang, S. Elemental Ferroelectricity and Antiferroelectricity in Group-V Monolayer. Adv. Funct. Mater. 2018, 28 (17), 1707383, DOI: 10.1002/adfm.201707383Google ScholarThere is no corresponding record for this reference.
- 28Tao, L. L.; Tsymbal, E. Y. Perspectives of spin-textured ferroelectrics. J. Phys. D: Appl. Phys. 2021, 54 (11), 113001, DOI: 10.1088/1361-6463/abcc25Google Scholar28https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXntVWht70%253D&md5=432683c0ea786e899c46ef6ed1d11615Perspectives of spin-textured ferroelectricsTao, L. L.; Tsymbal, Evgeny Y.Journal of Physics D: Applied Physics (2021), 54 (11), 113001CODEN: JPAPBE; ISSN:0022-3727. (IOP Publishing Ltd.)A review. Spin-orbit coupling (SOC) links the spin degree of freedom to the orbital motion of electrons in a solid and plays an important role in the emergence of new phys. phenomena. In non-centrosym. materials, the SOC locks the electron's spin direction to its momentum resulting in non-trivial spin textures in the reciprocal space. Depending on the crystal symmetry, the spin texture may exhibit Rashba, Dresselhaus, persistent, or more intricate configurations. In ferroelec. materials these spin textures are coupled to the ferroelec. polarization and thus can be controlled by its orientation and magnitude. This provides a promising platform to explore the coupling between spin, orbital, valley, and lattice degrees of freedoms in solids and opens a new direction for nonvolatile spintronic devices, such as a spin-field-effect transistor and a valley spin valve. Here, we review the recent advances in spin-texture physics of ferroelec. materials and outline possible device implications.
- 29Lee, H.; Im, J.; Jin, H. Emergence of the giant out-of-plane Rashba effect and tunable nanoscale persistent spin helix in ferroelectric SnTe thin films. Appl. Phys. Lett. 2020, 116 (2), 022411, DOI: 10.1063/1.5137753Google Scholar29https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXht1Glur4%253D&md5=20e15f0966a548f8b23eaa0e0a30708cEmergence of the giant out-of-plane Rashba effect and tunable nanoscale persistent spin helix in ferroelectric SnTe thin filmsLee, Hosik; Im, Jino; Jin, HosubApplied Physics Letters (2020), 116 (2), 022411CODEN: APPLAB; ISSN:0003-6951. (American Institute of Physics)A non-vanishing elec. field inside a non-centrosym. crystal transforms into a momentum-dependent magnetic field, namely, a spin-orbit field (SOF). SOFs are of great use in spintronics because they enable spin manipulation via the elec. field. At the same time, however, spintronic applications are severely limited by the SOF, as electrons traversing the SOF easily lose their spin information. Here, we propose that in-plane ferroelectricity in (001)-oriented SnTe thin films can support both elec. spin controllability and suppression of spin dephasing. The in-plane ferroelectricity produces a unidirectional out-of-plane Rashba SOF that can host a long-lived helical spin mode known as a persistent spin helix (PSH). Through direct coupling between the inversion asymmetry and the SOF, the ferroelec. switching reverses the out-of-plane Rashba SOF, giving rise to a maximally field-tunable PSH. Furthermore, the giant out-of-plane Rashba SOF seen in the SnTe thin films is linked to the nano-sized PSH, potentially reducing spintronic device sizes to the nanoscale. We combine the two ferroelec.-coupled degrees of freedom, longitudinal charge and transverse PSH, to design intersectional electro-spintronic transistors governed by non-volatile ferroelec. switching within nanoscale lateral and at.-thick vertical dimensions. (c) 2020 American Institute of Physics.
- 30Ugeda, M. M.; Bradley, A. J.; Zhang, Y.; Onishi, S.; Chen, Y.; Ruan, W.; Ojeda-Aristizabal, C.; Ryu, H.; Edmonds, M. T.; Tsai, H.-Z.; Riss, A.; Mo, S.-K.; Lee, D.; Zettl, A.; Hussain, Z.; Shen, Z.-X.; Crommie, M. F. Characterization of collective ground states in single-layer NbSe2. Nat. Phys. 2016, 12 (1), 92– 97, DOI: 10.1038/nphys3527Google Scholar30https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhslGmur7I&md5=4d4ccad8b04752bb41b37cb3371274a5Characterization of collective ground states in single-layer NbSe2Ugeda, Miguel M.; Bradley, Aaron J.; Zhang, Yi; Onishi, Seita; Chen, Yi; Ruan, Wei; Ojeda-Aristizabal, Claudia; Ryu, Hyejin; Edmonds, Mark T.; Tsai, Hsin-Zon; Riss, Alexander; Mo, Sung-Kwan; Lee, Dunghai; Zettl, Alex; Hussain, Zahid; Shen, Zhi-Xun; Crommie, Michael F.Nature Physics (2016), 12 (1), 92-97CODEN: NPAHAX; ISSN:1745-2473. (Nature Publishing Group)Layered transition metal dichalcogenides are ideal systems for exploring the effects of dimensionality on correlated electronic phases such as charge d. wave (CDW) order and supercond. In bulk NbSe2 a CDW sets in at TCDW = 33 K and supercond. sets in at Tc = 7.2 K. Below Tc these electronic states coexist but their microscopic formation mechanisms remain controversial. Here we present an electronic characterization study of a single two-dimensional (2D) layer of NbSe2 by means of low-temp. scanning tunnelling microscopy/spectroscopy (STM/STS), angle-resolved photoemission spectroscopy (ARPES), and elec. transport measurements. We demonstrate that 3 × 3 CDW order in NbSe2 remains intact in two dimensions. Supercond. also still remains in the 2D limit, but its onset temp. is depressed to 1.9 K. Our STS measurements at 5 K reveal a CDW gap of Δ = 4 meV at the Fermi energy, which is accessible by means of STS owing to the removal of bands crossing the Fermi level for a single layer. Our observations are consistent with the simplified (compared to bulk) electronic structure of single-layer NbSe2, thus providing insight into CDW formation and supercond. in this model strongly correlated system.
- 31Nakata, Y.; Sugawara, K.; Ichinokura, S.; Okada, Y.; Hitosugi, T.; Koretsune, T.; Ueno, K.; Hasegawa, S.; Takahashi, T.; Sato, T. Anisotropic band splitting in monolayer NbSe2: implications for superconductivity and charge density wave. npj 2D Mater. Appl. 2018, 2 (1), 12, DOI: 10.1038/s41699-018-0057-3Google ScholarThere is no corresponding record for this reference.
- 32Zhang, Y.; Sun, Y.; Yan, B. Berry curvature dipole in Weyl semimetal materials: An ab initio study. Phys. Rev. B: Condens. Matter Mater. Phys. 2018, 97 (4), 041101, DOI: 10.1103/PhysRevB.97.041101Google ScholarThere is no corresponding record for this reference.
- 33Lotsch, B. V. Vertical 2D Heterostructures. Annu. Rev. Mater. Res. 2015, 45 (1), 85– 109, DOI: 10.1146/annurev-matsci-070214-020934Google Scholar33https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhtFWqurvO&md5=b2f3d67ca2a7dae63284ed9000a3994dVertical 2D HeterostructuresLotsch, Bettina V.Annual Review of Materials Research (2015), 45 (), 85-109CODEN: ARMRCU; ISSN:1531-7331. (Annual Reviews)Graphene's legacy has become an integral part of today's condensed matter science and has equipped a whole generation of scientists with an armory of concepts and techniques that open up new perspectives for the postgraphene area. In particular, the judicious combination of 2D building blocks into vertical heterostructures has recently been identified as a promising route to rationally engineer complex multilayer systems and artificial solids with intriguing properties. The present review highlights recent developments in the rapidly emerging field of 2D nanoarchitectonics from a materials chem. perspective, with a focus on the types of heterostructures available, their assembly strategies, and their emerging properties. This overview is intended to bridge the gap between two major-yet largely disjunct-developments in 2D heterostructures, which are firmly rooted in solid-state chem. or physics. Although the underlying types of heterostructures differ with respect to their dimensions, layer alignment, and interfacial quality, there is common ground, and future synergies between the various assembly strategies are to be expected.
- 34Li, M.-Y.; Chen, C.-H.; Shi, Y.; Li, L.-J. Heterostructures based on two-dimensional layered materials and their potential applications. Mater. Today 2016, 19 (6), 322– 335, DOI: 10.1016/j.mattod.2015.11.003Google Scholar34https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhvVyqu73E&md5=c32cd974de826059f4c93ceb193bcc07Heterostructures based on two-dimensional layered materials and their potential applicationsLi, Ming-Yang; Chen, Chang-Hsiao; Shi, Yumeng; Li, Lain-JongMaterials Today (Oxford, United Kingdom) (2016), 19 (6), 322-335CODEN: MTOUAN; ISSN:1369-7021. (Elsevier Ltd.)The development of two-dimensional (2D) layered materials is driven by fundamental interest and their potential applications. Atomically thin 2D materials provide a wide range of basic building blocks with unique elec., optical, and thermal properties which do not exist in their bulk counterparts. The van der Waals interlayer interaction enables the possibility to exfoliate and reassemble different 2D materials into arbitrarily and vertically stacked heterostructures. Recently developed vapor phase growth of 2D materials further paves the way of directly synthesizing vertical and lateral heterojunctions. This review provides insights into the layered 2D heterostructures, with a concise introduction to preparative approaches for 2D materials and heterostructures. These unique 2D heterostructures have abundant implications for many potential applications.
- 35Zhao, A. L.; Li, H.; Hu, X. J.; Wang, C.; Zhang, H.; Lu, J. G.; Ruan, S. C.; Zeng, Y. J. Review of 2D group VA material-based heterostructures. J. Phys. D: Appl. Phys. 2020, 53 (29), 293002, DOI: 10.1088/1361-6463/ab810cGoogle Scholar35https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXhsFSrtr%252FK&md5=a41bbbf559154c140dde7a26f3c63c2cReview of 2D group VA material-based heterostructuresZhao, Ailun; Li, Hui; Hu, Xuejuan; Wang, Cong; Zhang, Han; Lu, Jianguo; Ruan, Shuangchen; Zeng, Yu-JiaJournal of Physics D: Applied Physics (2020), 53 (29), 293002CODEN: JPAPBE; ISSN:0022-3727. (IOP Publishing Ltd.)A review. The isolation of black phosphorus (BP) and extraordinary performance of the BP field-effect transistor have led to BP offering remarkable properties in the two-dimensional (2D) family. Along with BP, other group VA element materials have been demonstrated to possess superior electronic and optical properties. However, numerous challenges remain to be overcome in their practical applications. Heterostructures play a vital role in modern semiconductors, and 2D group VA materials provide the opportunity to fabricate novel heterostructures that are combined by van der Waals forces. Previous theor. and exptl. studies have indicated that constructing a heterostructure is a promising strategy to conquer the obstacles and boost the development of 2D group VA materials. In this paper, we summarize the recent progress in 2D group VA material-based heterostructures. Firstly, the crystal structures and fundamental elec. properties of 2D group VA materials are introduced. Thereafter, various heterostructures based on group VA materials are discussed. Finally, conclusions and the outlook on emerging group VA heterostructures are presented.
- 36Wang, Z. F.; Yao, M.-Y.; Ming, W.; Miao, L.; Zhu, F.; Liu, C.; Gao, C. L.; Qian, D.; Jia, J.-F.; Liu, F. Creation of helical Dirac fermions by interfacing two gapped systems of ordinary fermions. Nat. Commun. 2013, 4 (1), 1384, DOI: 10.1038/ncomms2387Google Scholar36https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADC%252BC3szhvF2nsw%253D%253D&md5=043cf56996e81863decff65d8c5d01c9Creation of helical Dirac fermions by interfacing two gapped systems of ordinary fermionsWang Z F; Yao Meng-Yu; Ming Wenmei; Miao Lin; Zhu Fengfeng; Liu Canhua; Gao C L; Qian Dong; Jia Jin-Feng; Liu FengNature communications (2013), 4 (), 1384 ISSN:.Topological insulators are a unique class of materials characterized by a Dirac cone state of helical Dirac fermions in the middle of a bulk gap. When the thickness of a three-dimensional topological insulator is reduced, however, the interaction between opposing surface states opens a gap that removes the helical Dirac cone, converting the material back to a normal system of ordinary fermions. Here we demonstrate, using density function theory calculations and experiments, that it is possible to create helical Dirac fermion state by interfacing two gapped films-a single bilayer Bi grown on a single quintuple layer Bi(2)Se(3) or Bi(2)Te(3). These extrinsic helical Dirac fermions emerge in predominantly Bi bilayer states, which are created by a giant Rashba effect with a coupling constant of ~4 eV·ÅA due to interfacial charge transfer. Our results suggest that this approach is a promising means to engineer topological insulator states on non-metallic surfaces.
- 37Yeom, H. W.; Kim, S. H.; Shin, W. J.; Jin, K.-H.; Park, J.; Kim, T.-H.; Kim, J. S.; Ishikawa, H.; Sakamoto, K.; Jhi, S.-H. Transforming a surface state of a topological insulator by a Bi capping layer. Phys. Rev. B: Condens. Matter Mater. Phys. 2014, 90 (23), 235401, DOI: 10.1103/PhysRevB.90.235401Google Scholar37https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXislWntbc%253D&md5=fba76577c174f741dd9c33b02243a97aTransforming a surface state of a topological insulator by a Bi capping layerYeom, Han Woong; Kim, Sung Hwan; Shin, Woo Jong; Jin, Kyung-Hwan; Park, Joonbum; Kim, Tae-Hwan; Kim, Jun Sung; Ishikawa, Hirotaka; Sakamoto, Kazuyuki; Jhi, Seung-HoonPhysical Review B: Condensed Matter and Materials Physics (2014), 90 (23), 235401/1-235401/5, 5 pp.CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)We introduce a distinct approach to engineer a topol. protected surface state of a topol. insulator. By covering the surface of a topol. insulator, Bi2Te2Se, with a Bi monolayer film, the original surface state is completely removed and three new spin helical surface states, originating from the Bi film, emerge with different dispersion and spin polarization, through a strong electron hybridization. These new states play the role of topol. surface states keeping the bulk topol. nature intact. This mechanism provides a way to create various different types of topol. protected electron channels on top of a single topol. insulator, possibly with tailored properties for various applications.
- 38Jin, K.-H.; Yeom, H. W.; Jhi, S.-H. Band structure engineering of topological insulator heterojunctions. Phys. Rev. B: Condens. Matter Mater. Phys. 2016, 93 (7), 075308, DOI: 10.1103/PhysRevB.93.075308Google ScholarThere is no corresponding record for this reference.
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Abstract
Figure 1
Figure 1. Atomic structure and electronic structure of the Bi(110) monolayer. (a) Top and side views of atomic structures of flat and puckered Bi(110) monolayer. (b, c) Calculated band structure of flat and puckered Bi(110) monolayer, respectively. The inset in c shows the BZ. The red (blue) arrow indicates the crossing point (SOC gap) along the X–M path. (d) 3D band plot of the puckered Bi(110) near the Γ point as indicated by the red line in the inset of (c). (e) Calculated band structure of the puckered Bi(110) monolayer under different out-of-plane electric fields, Ez = 0.0, 0.05, and 0.1 eV/Å. (f) Enlarged band structure as indicated by the red box in (e). (g) 3D band plot near the Γ point as indicated by the black box in (e).
Figure 2
Figure 2. Berry curvature properties of the Bi(110) monolayer. The calculated Berry curvature Ωz(k) of the puckered Bi(110) monolayer in the first Brillouin zone (BZ) at different Fermi energies; (a) E = 0 eV (all valence bands occupied), (b) E = −0.34 eV, and (c) E = −0.45 eV (parts of the valence bands are empty). The black arrow shows the direction of BCD vector Dy. (d) BC that is calculated along the −Y–G–Y line in under varying the out-of-plane electric fields (Ez). (e) Calculated BCD (Dy) of the puckered Bi(110) monolayer with varying Ez. The Fermi level (E = 0 eV) is based on the middle of the band gap of the Bi(110) monolayer.
Figure 3
Figure 3. Spin texture of the Bi(110) monolayer. (a) Spin resolved band structure of the puckered Bi(110) monolayer along the Γ–Y direction. (b) Spin texture measured at the constant-energy cut-off E = 0.37 eV as indicated by dashed line in (a). The in-plane polarization induces the unidirectional (z-direction) spin polarized spin texture. (c, d) Spin texture measured for the out-of-plane electric field Ez = 0.05 eV/Å and Ez = 0.1 eV/Å at the constant-energy cut-off E = 0.37 eV, respectively.
Figure 4
Figure 4. Bi/NbSe2 heterostructure model and the corresponding STM images. (a) Side and top views of the Bi/NbSe2 structural model consisting of a 6 × 3 Bi(110) monolayer on a 5√3 × 4 NbSe2 substrate. (b) STM morphology of Bi(110) films grown on a NbSe2 substrate (constant-current mode with Vbias = +0.5 V, lt = 100 pA, and 4.3 K). A narrow-area STM image of the Bi(110) 1L surface at (c) Vbias= +0.5 V, lt = 5000 pA, and 4.43 K and (d) Vbias= −0.5 V, lt = 5000 pA, and 4.43 K, respectively. (e) Atomically resolved STM image of the Bi(110) monolayer surface (left panel) for Vbias = +0.5 V and simulated STM image by integrating the orbitals from the Fermi level to 0.5 eV (right panel). (f) Atomically resolved STM image of the Bi(110) surface (left panel) for Vbias = −0.5 V and simulated STM image by integrating the orbitals from the Fermi level to −0.5 eV (right panel). (g) Experimental and simulated line profiles taken along the arrow marked in (e) and (f). (h) dI/dV/(I/V) spectra at fixed positions and projected DOS (PDOS) of the Bi atoms indicated by blue and red points in (a). The normalized dI/dV curves are taken from the bright and dark areas of the Moiré pattern as indicated by the blue and red points in the inset image, respectively. (i) Unfolded band structure and the corresponding spin-resolved band structure of the heterostructure Bi/NbSe2 model into the Brillouin zone of the Bi(110) monolayer unit cell for the equilibrium (d = 0 Å) and increased (d = 3 Å) bonding distance, respectively.
Figure 5
Figure 5. Reshaped band structure of the Bi/NbSe2 heterostructure. (a) Photoemission intensity and calculated band structure for pristine NbSe2, respectively. Green dashed lines overlaid on top of the ARPES map are the calculated band dispersions. (b) Photoemission intensity and unfolded band structure into primitive NbSe2 BZ for heterostructure Bi(110)/NbSe2, respectively.
References
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- 1Sodemann, I.; Fu, L. Quantum Nonlinear Hall Effect Induced by Berry Curvature Dipole in Time-Reversal Invariant Materials. Phys. Rev. Lett. 2015, 115 (21), 216806, DOI: 10.1103/PhysRevLett.115.2168061https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XkvF2jsro%253D&md5=02799fa18fe952a01b4c463b7d9dd719Quantum nonlinear Hall effect induced by berry curvature dipole in time-reversal invariant materialsSodemann, Inti; Fu, LiangPhysical Review Letters (2015), 115 (21), 216806/1-216806/5CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)It is well known that a nonvanishing Hall cond. requires broken time-reversal symmetry. However, in this work, we demonstrate that Hall-like currents can occur in second-order response to external elec. fields in a wide class of time-reversal invariant and inversion breaking materials, at both zero and twice the driving frequency. This nonlinear Hall effect has a quantum origin arising from the dipole moment of the Berry curvature in momentum space, which generates a net anomalous velocity when the system is in a current-carrying state. The nonlinear Hall coeff. is a rank-two pseudotensor, whose form is detd. by point group symmetry. We discus optimal conditions to observe this effect and propose candidate two- and three-dimensional materials, including topol. cryst. insulators, transition metal dichalcogenides, and Weyl semimetals.
- 2Xu, S.-Y.; Ma, Q.; Shen, H.; Fatemi, V.; Wu, S.; Chang, T.-R.; Chang, G.; Valdivia, A. M. M.; Chan, C.-K.; Gibson, Q. D.; Zhou, J.; Liu, Z.; Watanabe, K.; Taniguchi, T.; Lin, H.; Cava, R. J.; Fu, L.; Gedik, N.; Jarillo-Herrero, P. Electrically switchable Berry curvature dipole in the monolayer topological insulator WTe2. Nat. Phys. 2018, 14 (9), 900– 906, DOI: 10.1038/s41567-018-0189-62https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXht1Kltr3K&md5=19cd6eed84f5e743c96b95c5726363b6Electrically switchable Berry curvature dipole in the monolayer topological insulator WTe2Xu, Su-Yang; Ma, Qiong; Shen, Huitao; Fatemi, Valla; Wu, Sanfeng; Chang, Tay-Rong; Chang, Guoqing; Valdivia, Andres M. Mier; Chan, Ching-Kit; Gibson, Quinn D.; Zhou, Jiadong; Liu, Zheng; Watanabe, Kenji; Taniguchi, Takashi; Lin, Hsin; Cava, Robert J.; Fu, Liang; Gedik, Nuh; Jarillo-Herrero, PabloNature Physics (2018), 14 (9), 900-906CODEN: NPAHAX; ISSN:1745-2473. (Nature Research)Recent exptl. evidence for the quantum spin Hall (QSH) state in monolayer WTe2 has linked the fields of two-dimensional materials and topol. physics1-7. This two-dimensional topol. crystal also displays unconventional spin-torque8 and gate-tunable supercond.7. Whereas the realization of the QSH has demonstrated the nontrivial topol. of the electron wavefunctions of monolayer WTe2, the geometrical properties of the wavefunction, such as the Berry curvature9, remain unstudied. Here we utilize mid-IR optoelectronic microscopy to investigate the Berry curvature in monolayer WTe2. By optically exciting electrons across the inverted QSH gap, we observe an in-plane circular photogalvanic current even under normal incidence. The application of an out-of-plane displacement field allows further control of the direction and magnitude of the photocurrent. The obsd. photocurrent reveals a Berry curvature dipole that arises from the nontrivial wavefunctions near the inverted gap edge. The Berry curvature dipole and strong elec. field effect are enabled by the inverted band structure and tilted crystal lattice of monolayer WTe2. Such an elec. switchable Berry curvature dipole may facilitate the observation of a wide range of quantum geometrical phenomena such as the quantum nonlinear Hall10,11, orbital-Edelstein12 and chiral polaritonic effects13,14.
- 3Ma, Q.; Xu, S.-Y.; Shen, H.; MacNeill, D.; Fatemi, V.; Chang, T.-R.; Mier Valdivia, A. M.; Wu, S.; Du, Z.; Hsu, C.-H.; Fang, S.; Gibson, Q. D.; Watanabe, K.; Taniguchi, T.; Cava, R. J.; Kaxiras, E.; Lu, H.-Z.; Lin, H.; Fu, L.; Gedik, N.; Jarillo-Herrero, P. Observation of the nonlinear Hall effect under time-reversal-symmetric conditions. Nature 2019, 565 (7739), 337– 342, DOI: 10.1038/s41586-018-0807-63https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXisFCitbvF&md5=de981565b3691a251009e42fc4f4dcd8Observation of nonlinear Hall effect under time-reversal-symmetric conditionsMa, Qiong; Xu, Su-Yang; Shen, Huitao; MacNeill, David; Fatemi, Valla; Chang, Tay-Rong; Mier Valdivia, Andres M.; Wu, Sanfeng; Du, Zongzheng; Hsu, Chuang-Han; Fang, Shiang; Gibson, Quinn D.; Watanabe, Kenji; Taniguchi, Takashi; Cava, Robert J.; Kaxiras, Efthimios; Lu, Hai-Zhou; Lin, Hsin; Fu, Liang; Gedik, Nuh; Jarillo-Herrero, PabloNature (London, United Kingdom) (2019), 565 (7739), 337-342CODEN: NATUAS; ISSN:0028-0836. (Nature Research)The elec. Hall effect is the prodn., upon the application of an elec. field, of a transverse voltage under an out-of-plane magnetic field. Studies of the Hall effect have led to important breakthroughs, including the discoveries of Berry curvature and topol. Chern invariants1,2. The internal magnetization of magnets means that the elec. Hall effect can occur in the absence of an external magnetic field2; this 'anomalous' Hall effect is important for the study of quantum magnets2-7. The elec. Hall effect has rarely been studied in non-magnetic materials without external magnetic fields, owing to the constraint of time-reversal symmetry. However, only in the linear response regime-when the Hall voltage is linearly proportional to the external elec. field-does the Hall effect identically vanish as a result of time-reversal symmetry; the Hall effect in the nonlinear response regime is not subject to such symmetry constraints8-10. Here we report observations of the nonlinear Hall effect10 in elec. transport in bilayers of the non-magnetic quantum material WTe2 under time-reversal-sym. conditions. We show that an elec. current in bilayer WTe2 leads to a nonlinear Hall voltage in the absence of a magnetic field. The properties of this nonlinear Hall effect are distinct from those of the anomalous Hall effect in metals: the nonlinear Hall effect results in a quadratic, rather than linear, current-voltage characteristic and, in contrast to the anomalous Hall effect, the nonlinear Hall effect results in a much larger transverse than longitudinal voltage response, leading to a nonlinear Hall angle (the angle between the total voltage response and the applied elec. field) of nearly 90 degrees. We further show that the nonlinear Hall effect provides a direct measure of the dipole moment10 of the Berry curvature, which arises from layer-polarized Dirac fermions in bilayer WTe2. Our results demonstrate a new type of Hall effect and provide a way of detecting Berry curvature in non-magnetic quantum materials.
- 4Kang, K.; Li, T.; Sohn, E.; Shan, J.; Mak, K. F. Nonlinear anomalous Hall effect in few-layer WTe2. Nat. Mater. 2019, 18 (4), 324– 328, DOI: 10.1038/s41563-019-0294-74https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXmsVyqsL4%253D&md5=07c915ad3961df71bb748b0306ece579Nonlinear anomalous Hall effect in few-layer WTe2Kang, Kaifei; Li, Tingxin; Sohn, Egon; Shan, Jie; Mak, Kin FaiNature Materials (2019), 18 (4), 324-328CODEN: NMAACR; ISSN:1476-1122. (Nature Research)The Hall effect occurs only in systems with broken time-reversal symmetry, such as materials under an external magnetic field in the ordinary Hall effect and magnetic materials in the anomalous Hall effect (AHE)1. Here we show a nonlinear AHE in a non-magnetic material under zero magnetic field, in which the Hall voltage depends quadratically on the longitudinal current2-6. We observe the effect in few-layer Td-WTe2, a two-dimensional semimetal with broken inversion symmetry and only one mirror line in the crystal plane. Our angle-resolved elec. measurements reveal that the Hall voltage maximizes (vanishes) when the bias current is perpendicular (parallel) to the mirror line. The obsd. effect can be understood as an AHE induced by the bias current, which generates an out-of-plane magnetization. The temp. dependence of the Hall cond. further suggests that both the intrinsic Berry curvature dipole and extrinsic spin-dependent scatterings contribute to the obsd. nonlinear AHE.
- 5Isobe, H.; Xu, S.-Y.; Fu, L. High-frequency rectification via chiral Bloch electrons. Sci. Adv. 2020, 6 (13), eaay2497 DOI: 10.1126/sciadv.aay2497There is no corresponding record for this reference.
- 6Tao, L. L.; Tsymbal, E. Y. Persistent spin texture enforced by symmetry. Nat. Commun. 2018, 9 (1), 2763, DOI: 10.1038/s41467-018-05137-06https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADC%252BB3c%252Fpt1WjsA%253D%253D&md5=76809f9af9a74bd82fa1459c04d59083Persistent spin texture enforced by symmetryTao L L; Tsymbal Evgeny YNature communications (2018), 9 (1), 2763 ISSN:.Persistent spin texture (PST) is the property of some materials to maintain a uniform spin configuration in the momentum space. This property has been predicted to support an extraordinarily long spin lifetime of carriers promising for spintronics applications. Here, we predict that there exists a class of noncentrosymmetric bulk materials, where the PST is enforced by the nonsymmorphic space group symmetry of the crystal. Around certain high symmetry points in the Brillouin zone, the sublattice degrees of freedom impose a constraint on the effective spin-orbit field, which orientation remains independent of the momentum and thus maintains the PST. We illustrate this behavior using density-functional theory calculations for a handful of promising candidates accessible experimentally. Among them is the ferroelectric oxide BiInO3-a wide band gap semiconductor which sustains a PST around the conduction band minimum. Our results broaden the range of materials that can be employed in spintronics.
- 7Hu, L.; Huang, H.; Wang, Z.; Jiang, W.; Ni, X.; Zhou, Y.; Zielasek, V.; Lagally, M. G.; Huang, B.; Liu, F. Ubiquitous Spin-Orbit Coupling in a Screw Dislocation with High Spin Coherency. Phys. Rev. Lett. 2018, 121 (6), 066401, DOI: 10.1103/PhysRevLett.121.0664017https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXltFSnurs%253D&md5=8fed43df9c3d5d8b57f9c77ffbeb7d40Ubiquitous Spin-Orbit Coupling in a Screw Dislocation with High Spin CoherencyHu, Lin; Huang, Huaqing; Wang, Zhengfei; Jiang, W.; Ni, Xiaojuan; Zhou, Yinong; Zielasek, V.; Lagally, M. G.; Huang, Bing; Liu, FengPhysical Review Letters (2018), 121 (6), 066401CODEN: PRLTAO; ISSN:1079-7114. (American Physical Society)We theor. demonstrate that screw dislocation (SD), a 1D topol. defect widely present in semiconductors, exhibits ubiquitously a new form of spin-orbit coupling (SOC) effect. Differing from the widely known conventional 2D Rashba-Dresselhaus (RD) SOC effect that typically exists at surfaces or interfaces, the deep-level nature of SD-SOC states in semiconductors readily makes it an ideal SOC. Remarkably, the spin texture of 1D SD-SOC, pertaining to the inherent symmetry of SD, exhibits a significantly higher degree of spin coherency than the 2D RD-SOC. Moreover, the 1D SD-SOC can be tuned by ionicity in compd. semiconductors to ideally suppress spin relaxation, as demonstrated by comparative first-principles calcns. of SDs in Si/Ge, GaAs, and SiC. Our findings therefore open a new door to manipulating spin transport in semiconductors by taking advantage of an otherwise detrimental topol. defect.
- 8Li, X.; Zhang, S.; Huang, H.; Hu, L.; Liu, F.; Wang, Q. Unidirectional Spin–Orbit Interaction Induced by the Line Defect in Monolayer Transition Metal Dichalcogenides for High-Performance Devices. Nano Lett. 2019, 19 (9), 6005– 6012, DOI: 10.1021/acs.nanolett.9b018128https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhsFersrbI&md5=077416a96115fc009e70ea193e6aa18eUnidirectional Spin-Orbit Interaction Induced by the Line Defect in Monolayer Transition Metal Dichalcogenides for High-Performance DevicesLi, Xiaoyin; Zhang, Shunhong; Huang, Huaqing; Hu, Lin; Liu, Feng; Wang, QianNano Letters (2019), 19 (9), 6005-6012CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)Spin-orbit (SO) interaction is an indispensable element in the field of spintronics for effectively manipulating the spin of carriers. However, in cryst. solids, the momentum-dependent SO effective magnetic field generally results in spin randomization by a process known as the Dyakonov-Perel spin relaxation, leading to the loss of spin information. To overcome this obstacle, the persistent spin helix (PSH) state with a unidirectional SO field was proposed but difficult to achieve in real materials. Here, on the basis of first-principles calcns. and tight-binding model anal., we report for the first time a unidirectional SO field in monolayer transition metal dichalcogenides (TMDs, MX2, M = Mo, W; and X = S, Se) induced by two parallel chalcogen vacancy lines. By changing the relative positions of the two vacancy lines, the direction of the SO field can be tuned from x to y. Moreover, using k·p perturbation theory and group theory anal., we demonstrate that the emerging unidirectional SO field is subject to both the structural symmetry and 1D nature of such defects engineered in 2D TMDs. In particular, through transport calcns., we confirm that the predicted SO states carry highly coherent spin current. Our findings shed new light on creating PSH states for high-performance spintronic devices.
- 9Cui, C.; Xue, F.; Hu, W.-J.; Li, L.-J. Two-dimensional materials with piezoelectric and ferroelectric functionalities. npj 2D Mater. Appl. 2018, 2 (1), 18, DOI: 10.1038/s41699-018-0063-5There is no corresponding record for this reference.
- 10Autere, A.; Jussila, H.; Dai, Y.; Wang, Y.; Lipsanen, H.; Sun, Z. Nonlinear Optics with 2D Layered Materials. Adv. Mater. 2018, 30 (24), 1705963, DOI: 10.1002/adma.201705963There is no corresponding record for this reference.
- 11Avsar, A.; Ochoa, H.; Guinea, F.; Özyilmaz, B.; van Wees, B. J.; Vera-Marun, I. J. Colloquium: Spintronics in graphene and other two-dimensional materials. Rev. Mod. Phys. 2020, 92 (2), 021003, DOI: 10.1103/RevModPhys.92.02100311https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXitFWnsb3I&md5=a30d987f298212590a1d11c91714f4aaColloquium: Spintronics in graphene and other two-dimensional materialsAvsar, A.; Ochoa, H.; Guinea, F.; Ozyilmaz, B.; van Wees, B. J.; Vera-Marun, I. J.Reviews of Modern Physics (2020), 92 (2), 021003CODEN: RMPHAT; ISSN:1539-0756. (American Physical Society)A review. After the first unequivocal demonstration of spin transport in graphene [Tombros et al., Nature (London) 448, 571-574 (2007)], surprisingly at room temp., it was quickly realized that this novel material was relevant for both fundamental spintronics and future applications. In the decade since, exciting results have made the field of graphene spintronics blossom, and a second generation of studies has extended to new two-dimensional (2D) compds. This Colloquium reviews recent theor. and exptl. advances on electronic spin transport in graphene and related 2D materials, focusing on emergent phenomena in van der Waals heterostructures and the new perspectives provided by them. These phenomena include proximity-enabled spin-orbit effects, the coupling of electronic spin to light, elec. tunability, and 2D magnetism.
- 12You, J.-S.; Fang, S.; Xu, S.-Y.; Kaxiras, E.; Low, T. Berry curvature dipole current in the transition metal dichalcogenides family. Phys. Rev. B: Condens. Matter Mater. Phys. 2018, 98 (12), 121109, DOI: 10.1103/PhysRevB.98.121109There is no corresponding record for this reference.
- 13Du, Z. Z.; Wang, C. M.; Lu, H.-Z.; Xie, X. C. Band Signatures for Strong Nonlinear Hall Effect in Bilayer WTe2. Phys. Rev. Lett. 2018, 121 (26), 266601, DOI: 10.1103/PhysRevLett.121.26660113https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXlslCqtLo%253D&md5=1400ee25ef1075104a72f7b69403cbdaBand signatures for strong nonlinear hall effect in bilayer WTe2Du, Z. Z.; Wang, C. M.; Lu, Hai-Zhou; Xie, X. C.Physical Review Letters (2018), 121 (26), 266601/1-266601/6CODEN: PRLTAO; ISSN:1079-7114. (American Physical Society)Unconventional responses upon breaking discrete or crystal symmetries open avenues for exploring emergent phys. systems and materials. By breaking inversion symmetry, a nonlinear Hall signal can be obsd., even in the presence of time-reversal symmetry, quite different from the conventional Hall effects. Low-symmetry two-dimensional materials are promising candidates for the nonlinear Hall effect, but it is less known when a strong nonlinear Hall signal can be measured, in particular, its connections with the band-structure properties. By using model anal., we find prominent nonlinear Hall signals near tilted band anticrossings and band inversions. These band signatures can be used to explain the strong nonlinear Hall effect in the recent expts. on two-dimensional WTe2. This Letter will be instructive not only for analyzing the transport signatures of the nonlinear Hall effect but also for exploring unconventional responses in emergent materials.
- 14Kim, J.; Kim, K.-W.; Shin, D.; Lee, S.-H.; Sinova, J.; Park, N.; Jin, H. Prediction of ferroelectricity-driven Berry curvature enabling charge- and spin-controllable photocurrent in tin telluride monolayers. Nat. Commun. 2019, 10 (1), 3965, DOI: 10.1038/s41467-019-11964-614https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADC%252BB3MrkvVChtA%253D%253D&md5=c77bc43aab98e557dd8600eb670b05ddPrediction of ferroelectricity-driven Berry curvature enabling charge- and spin-controllable photocurrent in tin telluride monolayersKim Jeongwoo; Shin Dongbin; Park Noejung; Jin Hosub; Kim Jeongwoo; Kim Kyoung-Whan; Kim Kyoung-Whan; Sinova Jairo; Lee Sang-Hoon; Sinova JairoNature communications (2019), 10 (1), 3965 ISSN:.In symmetry-broken crystalline solids, pole structures of Berry curvature (BC) can emerge, and they have been utilized as a versatile tool for controlling transport properties. For example, the monopole component of the BC is induced by the time-reversal symmetry breaking, and the BC dipole arises from a lack of inversion symmetry, leading to the anomalous Hall and nonlinear Hall effects, respectively. Based on first-principles calculations, we show that the ferroelectricity in a tin telluride monolayer produces a unique BC distribution, which offers charge- and spin-controllable photocurrents. Even with the sizable band gap, the ferroelectrically driven BC dipole is comparable to those of small-gap topological materials. By manipulating the photon handedness and the ferroelectric polarization, charge and spin circular photogalvanic currents are generated in a controllable manner. The ferroelectricity in group-IV monochalcogenide monolayers can be a useful tool to control the BC dipole and the nonlinear optoelectronic responses.
- 15Absor, M. A. U.; Ishii, F. Intrinsic persistent spin helix state in two-dimensional group-IV monochalcogenide MX monolayers (M = Sn or Ge and X = S, Se, or Te). Phys. Rev. B: Condens. Matter Mater. Phys. 2019, 100 (11), 115104, DOI: 10.1103/PhysRevB.100.115104There is no corresponding record for this reference.
- 16Sławińska, J.; Cerasoli, F. T.; Gopal, P.; Costa, M.; Curtarolo, S.; Buongiorno Nardelli, M. Ultrathin SnTe films as a route towards all-in-one spintronics devices. 2D Mater. 2020, 7 (2), 025026, DOI: 10.1088/2053-1583/ab6f7a16https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXitFCiurfF&md5=82a2a6f59ba19ccbf403f12536e4e8eeUltrathin SnTe films as a route towards all-in-one spintronics devicesSlawinska, Jagoda; Cerasoli, Frank T.; Gopal, Priya; Costa, Marcio; Curtarolo, Stefano; Nardelli, Marco Buongiorno2D Materials (2020), 7 (2), 025026CODEN: DMATB7; ISSN:2053-1583. (IOP Publishing Ltd.)Spin transistors based on a semiconducting channel attached to ferromagnetic electrodes suffer from fast spin decay and extremely low spin injection/detection efficiencies. Here, we propose an alternative all-in-one spin device whose operation principle relies on elec. manipulation of the spin lifetime in two-dimensional (2D) SnTe, in which the sizable spin Hall effect eliminates the need for using ferromagnets. In particular, we explore the persistent spin texture (PST) intrinsically present in the ferroelec. phase which protects the spin from decoherence and supports extraordinarily long spin lifetime. Our first-principles calcns. followed by symmetry arguments revealed that such a spin wave mode can be externally detuned by perpendicular elec. field, leading to spin randomization and decrease in spin lifetime. We further extend our anal. to ultrathin SnTe films and confirm the emergence of PST as well as a moderate enhancement of intrinsic spin Hall cond. The recent room-temp. observation of the ferroelec. phase in 2D-SnTe suggests that novel all-elec. spintronics devices are within reach.
- 17Bian, G.; Wang, X.; Miller, T.; Chiang, T. C.; Kowalczyk, P. J.; Mahapatra, O.; Brown, S. A. First-principles and spectroscopic studies of Bi(110) films: Thickness-dependent Dirac modes and property oscillations. Phys. Rev. B: Condens. Matter Mater. Phys. 2014, 90 (19), 195409, DOI: 10.1103/PhysRevB.90.19540917https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhsVKmtbg%253D&md5=3d171b7880915307928baf756f8ea8e9First-principles and spectroscopic studies of Bi(110) films: thickness-dependent Dirac modes and property oscillationsBian, G.; Wang, X.; Miller, T.; Chiang, T.-C.; Kowalczyk, P. J.; Mahapatra, O.; Brown, S. A.Physical Review B: Condensed Matter and Materials Physics (2014), 90 (19), 195409/1-195409/7, 7 pp.CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)The electronic structure of Bi(110) thin films as a function of film thickness is investigated by first-principles calcns., angle-resolved photoemission spectroscopy, and scanning tunneling microscopy. Energy minimization in the calcn. reveals significant at. relaxation and rebonding at the surface. The calcd. surface energy for the relaxed structures indicates that films consisting of odd nos. of at. layers are inherently unstable and tend to bifurcate into film domains consisting of neighboring even nos. of at. layers. This theor. trend agrees with exptl. observations. The results can be explained by the presence of unsatd. pz dangling bonds on the surfaces of films of odd-numbered at. layers only. These pz dangling bonds form a Dirac-cone feature near the Fermi level at the ‾M point as a consequence of the interplay of mirror symmetry and spin-orbit coupling. Films consisting of even nos. of at. layers exhibit a band gap at ‾M instead.
- 18Lu, Y.; Zhou, D.; Chang, G.; Guan, S.; Chen, W.; Jiang, Y.; Jiang, J.; Wang, X.-s.; Yang, S. A.; Feng, Y. P.; Kawazoe, Y.; Lin, H. Multiple unpinned Dirac points in group-Va single-layers with phosphorene structure. npj Comput. Mater. 2016, 2 (1), 16011, DOI: 10.1038/npjcompumats.2016.11There is no corresponding record for this reference.
- 19Pumera, M.; Sofer, Z. 2D Monoelemental Arsenene, Antimonene, and Bismuthene: Beyond Black Phosphorus. Adv. Mater. 2017, 29 (21), 1605299, DOI: 10.1002/adma.201605299There is no corresponding record for this reference.
- 20Jin, K.-H.; Huang, H.; Wang, Z.; Liu, F. A 2D nonsymmorphic Dirac semimetal in a chemically modified group-VA monolayer with a black phosphorene structure. Nanoscale 2019, 11 (15), 7256– 7262, DOI: 10.1039/C9NR00906J20https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXltFGntLY%253D&md5=26d94c1868514770fd3d5640d0c297afA 2D nonsymmorphic Dirac semimetal in a chemically modified group-VA monolayer with a black phosphorene structureJin, Kyung-Hwan; Huang, Huaqing; Wang, Zhengfei; Liu, FengNanoscale (2019), 11 (15), 7256-7262CODEN: NANOHL; ISSN:2040-3372. (Royal Society of Chemistry)A symmetry-protected 2D Dirac semimetal has attracted intense interest for its intriguing material properties. Here, we report a 2D nonsymmorphic Dirac semimetal state in a chem. modified group-VA 2D puckered structure. Based on first-principles calcns., we demonstrate the existence of 2D Dirac fermions in a one-side modified phosphorene structure in two different types: one with a Dirac nodal line (DNL) structure for light elements with negligible spin-orbit coupling (SOC) and the other having an hourglass band protected by a nonsymmorphic symmetry for heavy elements with strong SOC. In the absence of SOC, the DNL exhibits an anisotropic behavior and unique electronic properties, such as const. d. of states. The Dirac node is protected from gap opening by the nonsymmorphic space group symmetry. In the presence of SOC, the DNL states split and form an hourglass-shaped dispersion due to the broken inversion symmetry and the Rashba SOC interaction. Moreover, around certain high symmetry points in the Brillouin zone, the spin orientation is enforced to be along a specific direction. We construct an effective tight-binding model to characterize the 2D nonsymmorphic Dirac states. Our result provides a promising material platform for exploring the intriguing properties of essential nodal-line and nodal-point fermions in 2D systems.
- 21Peng, L.; Qiao, J.; Xian, J.-J.; Pan, Y.; Ji, W.; Zhang, W.; Fu, Y.-S. Unusual Electronic States and Superconducting Proximity Effect of Bi Films Modulated by a NbSe2 Substrate. ACS Nano 2019, 13 (2), 1885– 1892, DOI: 10.1021/acsnano.8b0805121https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhsFajtLs%253D&md5=ad52c19437e320c7b22a220f6fef602eUnusual Electronic States and Superconducting Proximity Effect of Bi Films Modulated by a NbSe2 SubstratePeng, Lang; Qiao, Jingsi; Xian, Jing-Jing; Pan, Yuhao; Ji, Wei; Zhang, Wenhao; Fu, Ying-ShuangACS Nano (2019), 13 (2), 1885-1892CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)Heterostructures of two-dimensional layered materials can be functionalized with exotic phenomena that are unpresented with each constituting component. The interface effect plays a key role in detg. the electronic properties of the heterostructure, whose characterization requires a correlation with the morphol. with at.-scale precision. Here, we report an investigation on the electronic properties of few-layer Bi(110) films mediated by a NbSe2 substrate. By utilizing scanning tunneling microscopy and spectroscopy, we show a significant variation of the d. of states at different Bi film thicknesses, resulting in an unusual superconducting proximity effect that deviates from the conventional monotonous decay behavior. Moreover, the electronic states of the Bi films are also prominently modulated by the Moir´e pattern spatially. With first-principles calcns., we illuminate these findings as the results of covalent-like quasi-bonds formed at the Bi/NbSe2 interface, which profoundly alter the charge distributions in the Bi films. Our study indicates a viable way of modulating the electronic properties of ultrathin films by quasi-covalent interfacial couplings beyond conventional van der Waals interactions.
- 22Dong, X.; Li, Y.; Li, J.; Peng, X.; Qiao, L.; Chen, D.; Yang, H.; Xiong, X.; Wang, Q.; Li, X.; Duan, J.; Han, J.; Xiao, W. Epitaxial Growth and Structural Properties of Bi(110) Thin Films on TiSe2 Substrates. J. Phys. Chem. C 2019, 123 (22), 13637– 13641, DOI: 10.1021/acs.jpcc.9b0192322https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXptlelsLs%253D&md5=221079a78aceb8c02eb9afd82caad6bfEpitaxial Growth and Structural Properties of Bi(110) Thin Films on TiSe2 SubstratesDong, Xu; Li, Yongkai; Li, Ji; Peng, Xianglin; Qiao, Lu; Chen, Dongyun; Yang, Huixia; Xiong, Xiaolu; Wang, Qinsheng; Li, Xiang; Duan, Junxi; Han, Junfeng; Xiao, WendeJournal of Physical Chemistry C (2019), 123 (22), 13637-13641CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)We report the growth and structural properties of Bi thin films on TiSe2 substrates by using a low-temp. scanning tunneling microscope. Extended Bi(110) thin films are formed on the TiSe2 substrates and adopt a distorted black-phosphorus structure at room temp. (RT). The diagonal of the Bi(110) rectangular unit cell is parallel to the close-packed direction of the top-layer Se atoms of the TiSe2 substrates, resulting in the formation of a stripe-shaped commensurate moir´e pattern with a periodicity of ∼38.5 Å at RT. Meanwhile, the charge d. wave phase transition of the TiSe2 substrate and the different coeffs. of thermal expansion of Bi(110) and TiSe2 lead to the formation of a quasi-hexagonal incommensurate moir´e pattern with a periodicity of 14.5 Å at 77 K. In particular, the combination of domains with twisting angles of 30° or 60° results in the formation of various domain boundaries. Our work is very helpful for understanding and tuning the structural and electronic properties of epitaxial Bi(110) thin films.
- 23Ju, S.; Wu, M.; Yang, H.; Wang, N.; Zhang, Y.; Wu, P.; Wang, P.; Zhang, B.; Mu, K.; Li, Y.; Guan, D.; Qian, D.; Lu, F.; Liu, D.; Wang, W.-H.; Chen, X.; Sun, Z. Band Structures of Ultrathin Bi(110) Films on Black Phosphorus Substrates Using Angle-Resolved Photoemission Spectroscopy. Chin. Phys. Lett. 2018, 35 (7), 077102, DOI: 10.1088/0256-307X/35/7/07710223https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXlsVGqtL0%253D&md5=c9386d7364f8c7b86305a996e37312eaBand structures of ultrathin Bi(110) films on black phosphorus substrates using angle-resolved photoemission spectroscopyJu, Sailong; Wu, Maokun; Yang, Hao; Wang, Naizhou; Zhang, Yingying; Wu, Peng; Wang, Pengdong; Zhang, Bo; Mu, Kejun; Li, Yaoyi; Guan, Dandan; Qian, Dong; Lu, Feng; Liu, Dayong; Wang, Wei-Hua; Chen, Xianhui; Sun, ZheChinese Physics Letters (2018), 35 (7), 077102/1-077102/5CODEN: CPLEEU; ISSN:1741-3540. (IOP Publishing Ltd.)The band structures of two-monolayer Bi(110) films on black phosphorus substrates are studied using angleresolved photoemission spectroscopy. Within the band gap of bulk black phosphorus, the electronic states near the Fermi level are dominated by the Bi(110) film. The band dispersions revealed by our data suggest that the orientation of the Bi(110) film is aligned with the black phosphorus substrate. The electronic structures of the Bi(110) film strongly deviate from the band calcns. of the free-standing Bi(110) film, suggesting that the substrate can significantly affect the electronic states in the Bi(110) film. Our data show that there are no non-trivial electronic states in Bi(110) films grown on black phosphorus substrates.
- 24Lu, Y.; Xu, W.; Zeng, M.; Yao, G.; Shen, L.; Yang, M.; Luo, Z.; Pan, F.; Wu, K.; Das, T.; He, P.; Jiang, J.; Martin, J.; Feng, Y. P.; Lin, H.; Wang, X.-s. Topological Properties Determined by Atomic Buckling in Self-Assembled Ultrathin Bi(110). Nano Lett. 2015, 15 (1), 80– 87, DOI: 10.1021/nl502997v24https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXitFaqsLfP&md5=c7c2e7bc71184fb0202bad73254c3fd8Topological Properties Determined by Atomic Buckling in Self-Assembled Ultrathin Bi(110)Lu, Yunhao; Xu, Wentao; Zeng, Mingang; Yao, Guanggeng; Shen, Lei; Yang, Ming; Luo, Ziyu; Pan, Feng; Wu, Ke; Das, Tanmoy; He, Pimo; Jiang, Jianzhong; Martin, Jens; Feng, Yuan Ping; Lin, Hsin; Wang, Xue-senNano Letters (2015), 15 (1), 80-87CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)Topol. insulators (TIs) are a new type of electronic materials in which the nontrivial insulating bulk band topol. governs conducting boundary states with embedded spin-momentum locking. Such edge states are more robust in a two-dimensional (2D) TI against scattering by nonmagnetic impurities than in its three-dimensional (3D) variant, because in 2D the two helical edge states are protected from the only possible backscattering. This makes the 2D TI family a better candidate for coherent spin transport and related applications. While several 3D TIs are already synthesized exptl., phys. realization of 2D TI is so far limited to hybrid quantum wells with a tiny bandgap that does not survive temps. above 10 K. Here, combining first-principles calcns. and scanning tunneling microscopy/spectroscopy (STM/STS) exptl. studies, we report nontrivial 2D TI phases in 2-monolayer (2-ML) and 4-ML Bi(110) films with large and tunable bandgaps detd. by at. buckling of Bi(110) films. The gapless edge states are exptl. detected within the insulating bulk gap at 77 K. The band topol. of ultrathin Bi(110) films is sensitive to at. buckling. Such buckling is sensitive to charge doping and could be controlled by choosing different substrates on which Bi(110) films are grown.
- 25Kokubo, I.; Yoshiike, Y.; Nakatsuji, K.; Hirayama, H. Ultrathin Bi(110) films on Si(111)√3×√3-B substrates. Phys. Rev. B: Condens. Matter Mater. Phys. 2015, 91 (7), 075429, DOI: 10.1103/PhysRevB.91.07542925https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXptlClt7g%253D&md5=0c5a82b472d10904bc05066d3f5f9152Ultrathin Bi(110) films on Si(111)√ ×3 √3-B substratesKokubo, Ikuya; Yoshiike, Yusaku; Nakatsuji, Kan; Hirayama, HiroyukiPhysical Review B: Condensed Matter and Materials Physics (2015), 91 (7), 075429/1-075429/7CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)We studied the structure of ultrathin Bi(110) films on Si(111)√3 × √3-B substrates using scanning tunneling microscopy. Atomically flat Bi islands were nucleated on the substrates at room temp. The edges of these islands were parallel to the short side of the Bi(110) rectangular unit cell. The islands extended along six specific orientations because the rectangular Bi(110) and rhombus √3 × √3 unit cells were commensurate at the interface. Bi(110) domains along different orientations coexisted and formed various domain boundary structures on the wide terraces of the islands. In particular, the domains along ±87° from the {‾110} direction were connected perfectly on an at. scale by changing the direction of the p-like bond of the in-plane zigzag chains locally at the straight domain boundary. No exclusive preference for the black phosphorus structure was obsd. for the Bi(110) ultrathin films, in contrast to the islands grown on the Si(111)7 × 7 substrate.
- 26Zhang, Y.; van den Brink, J.; Felser, C.; Yan, B. H. Electrically tuneable nonlinear anomalous Hall effect in two-dimensional transition-metal dichalcogenides WTe2 and MoTe2. 2D Mater. 2018, 5 (4), 044001, DOI: 10.1088/2053-1583/aad1ae26https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhvFeiu7nM&md5=d0dfb6c1eaffd3aec1d7a99b9ce543eaElectrically tuneable nonlinear anomalous Hall effect in two-dimensional transition-metal dichalcogenides WTe2 and MoTe2Zhang, Yang; van den Brink, Jeroen; Felser, Claudia; Yan, Binghai2D Materials (2018), 5 (4), 044001CODEN: DMATB7; ISSN:2053-1583. (IOP Publishing Ltd.)We studied the nonlinear elec. response in WTe2 and MoTe2 monolayers. When the inversion symmetry is breaking but the the time-reversal symmetry is preserved, a second-order Hall effect called the nonlinear anomalous Hall effect (NLAHE) emerges owing to the nonzero Berry curvature on the nonequil. Fermi surface. We reveal a strong NLAHE with a Hall-voltage that is quadratic with respect to the longitudinal current. The optimal current direction is normal to the mirror plane in these two-dimensional (2D) materials. The NLAHE can be sensitively tuned by an out-of-plane elec. field, which induces a transition from a topol. insulator to a normal insulator. Crossing the crit. transition point, the magnitude of the NLAHE increases, and its sign is reversed. Our work paves the way to discover exotic nonlinear phenomena in inversion-symmetry-breaking 2D materials.
- 27Xiao, C.; Wang, F.; Yang, S. A.; Lu, Y.; Feng, Y.; Zhang, S. Elemental Ferroelectricity and Antiferroelectricity in Group-V Monolayer. Adv. Funct. Mater. 2018, 28 (17), 1707383, DOI: 10.1002/adfm.201707383There is no corresponding record for this reference.
- 28Tao, L. L.; Tsymbal, E. Y. Perspectives of spin-textured ferroelectrics. J. Phys. D: Appl. Phys. 2021, 54 (11), 113001, DOI: 10.1088/1361-6463/abcc2528https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXntVWht70%253D&md5=432683c0ea786e899c46ef6ed1d11615Perspectives of spin-textured ferroelectricsTao, L. L.; Tsymbal, Evgeny Y.Journal of Physics D: Applied Physics (2021), 54 (11), 113001CODEN: JPAPBE; ISSN:0022-3727. (IOP Publishing Ltd.)A review. Spin-orbit coupling (SOC) links the spin degree of freedom to the orbital motion of electrons in a solid and plays an important role in the emergence of new phys. phenomena. In non-centrosym. materials, the SOC locks the electron's spin direction to its momentum resulting in non-trivial spin textures in the reciprocal space. Depending on the crystal symmetry, the spin texture may exhibit Rashba, Dresselhaus, persistent, or more intricate configurations. In ferroelec. materials these spin textures are coupled to the ferroelec. polarization and thus can be controlled by its orientation and magnitude. This provides a promising platform to explore the coupling between spin, orbital, valley, and lattice degrees of freedoms in solids and opens a new direction for nonvolatile spintronic devices, such as a spin-field-effect transistor and a valley spin valve. Here, we review the recent advances in spin-texture physics of ferroelec. materials and outline possible device implications.
- 29Lee, H.; Im, J.; Jin, H. Emergence of the giant out-of-plane Rashba effect and tunable nanoscale persistent spin helix in ferroelectric SnTe thin films. Appl. Phys. Lett. 2020, 116 (2), 022411, DOI: 10.1063/1.513775329https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXht1Glur4%253D&md5=20e15f0966a548f8b23eaa0e0a30708cEmergence of the giant out-of-plane Rashba effect and tunable nanoscale persistent spin helix in ferroelectric SnTe thin filmsLee, Hosik; Im, Jino; Jin, HosubApplied Physics Letters (2020), 116 (2), 022411CODEN: APPLAB; ISSN:0003-6951. (American Institute of Physics)A non-vanishing elec. field inside a non-centrosym. crystal transforms into a momentum-dependent magnetic field, namely, a spin-orbit field (SOF). SOFs are of great use in spintronics because they enable spin manipulation via the elec. field. At the same time, however, spintronic applications are severely limited by the SOF, as electrons traversing the SOF easily lose their spin information. Here, we propose that in-plane ferroelectricity in (001)-oriented SnTe thin films can support both elec. spin controllability and suppression of spin dephasing. The in-plane ferroelectricity produces a unidirectional out-of-plane Rashba SOF that can host a long-lived helical spin mode known as a persistent spin helix (PSH). Through direct coupling between the inversion asymmetry and the SOF, the ferroelec. switching reverses the out-of-plane Rashba SOF, giving rise to a maximally field-tunable PSH. Furthermore, the giant out-of-plane Rashba SOF seen in the SnTe thin films is linked to the nano-sized PSH, potentially reducing spintronic device sizes to the nanoscale. We combine the two ferroelec.-coupled degrees of freedom, longitudinal charge and transverse PSH, to design intersectional electro-spintronic transistors governed by non-volatile ferroelec. switching within nanoscale lateral and at.-thick vertical dimensions. (c) 2020 American Institute of Physics.
- 30Ugeda, M. M.; Bradley, A. J.; Zhang, Y.; Onishi, S.; Chen, Y.; Ruan, W.; Ojeda-Aristizabal, C.; Ryu, H.; Edmonds, M. T.; Tsai, H.-Z.; Riss, A.; Mo, S.-K.; Lee, D.; Zettl, A.; Hussain, Z.; Shen, Z.-X.; Crommie, M. F. Characterization of collective ground states in single-layer NbSe2. Nat. Phys. 2016, 12 (1), 92– 97, DOI: 10.1038/nphys352730https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhslGmur7I&md5=4d4ccad8b04752bb41b37cb3371274a5Characterization of collective ground states in single-layer NbSe2Ugeda, Miguel M.; Bradley, Aaron J.; Zhang, Yi; Onishi, Seita; Chen, Yi; Ruan, Wei; Ojeda-Aristizabal, Claudia; Ryu, Hyejin; Edmonds, Mark T.; Tsai, Hsin-Zon; Riss, Alexander; Mo, Sung-Kwan; Lee, Dunghai; Zettl, Alex; Hussain, Zahid; Shen, Zhi-Xun; Crommie, Michael F.Nature Physics (2016), 12 (1), 92-97CODEN: NPAHAX; ISSN:1745-2473. (Nature Publishing Group)Layered transition metal dichalcogenides are ideal systems for exploring the effects of dimensionality on correlated electronic phases such as charge d. wave (CDW) order and supercond. In bulk NbSe2 a CDW sets in at TCDW = 33 K and supercond. sets in at Tc = 7.2 K. Below Tc these electronic states coexist but their microscopic formation mechanisms remain controversial. Here we present an electronic characterization study of a single two-dimensional (2D) layer of NbSe2 by means of low-temp. scanning tunnelling microscopy/spectroscopy (STM/STS), angle-resolved photoemission spectroscopy (ARPES), and elec. transport measurements. We demonstrate that 3 × 3 CDW order in NbSe2 remains intact in two dimensions. Supercond. also still remains in the 2D limit, but its onset temp. is depressed to 1.9 K. Our STS measurements at 5 K reveal a CDW gap of Δ = 4 meV at the Fermi energy, which is accessible by means of STS owing to the removal of bands crossing the Fermi level for a single layer. Our observations are consistent with the simplified (compared to bulk) electronic structure of single-layer NbSe2, thus providing insight into CDW formation and supercond. in this model strongly correlated system.
- 31Nakata, Y.; Sugawara, K.; Ichinokura, S.; Okada, Y.; Hitosugi, T.; Koretsune, T.; Ueno, K.; Hasegawa, S.; Takahashi, T.; Sato, T. Anisotropic band splitting in monolayer NbSe2: implications for superconductivity and charge density wave. npj 2D Mater. Appl. 2018, 2 (1), 12, DOI: 10.1038/s41699-018-0057-3There is no corresponding record for this reference.
- 32Zhang, Y.; Sun, Y.; Yan, B. Berry curvature dipole in Weyl semimetal materials: An ab initio study. Phys. Rev. B: Condens. Matter Mater. Phys. 2018, 97 (4), 041101, DOI: 10.1103/PhysRevB.97.041101There is no corresponding record for this reference.
- 33Lotsch, B. V. Vertical 2D Heterostructures. Annu. Rev. Mater. Res. 2015, 45 (1), 85– 109, DOI: 10.1146/annurev-matsci-070214-02093433https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhtFWqurvO&md5=b2f3d67ca2a7dae63284ed9000a3994dVertical 2D HeterostructuresLotsch, Bettina V.Annual Review of Materials Research (2015), 45 (), 85-109CODEN: ARMRCU; ISSN:1531-7331. (Annual Reviews)Graphene's legacy has become an integral part of today's condensed matter science and has equipped a whole generation of scientists with an armory of concepts and techniques that open up new perspectives for the postgraphene area. In particular, the judicious combination of 2D building blocks into vertical heterostructures has recently been identified as a promising route to rationally engineer complex multilayer systems and artificial solids with intriguing properties. The present review highlights recent developments in the rapidly emerging field of 2D nanoarchitectonics from a materials chem. perspective, with a focus on the types of heterostructures available, their assembly strategies, and their emerging properties. This overview is intended to bridge the gap between two major-yet largely disjunct-developments in 2D heterostructures, which are firmly rooted in solid-state chem. or physics. Although the underlying types of heterostructures differ with respect to their dimensions, layer alignment, and interfacial quality, there is common ground, and future synergies between the various assembly strategies are to be expected.
- 34Li, M.-Y.; Chen, C.-H.; Shi, Y.; Li, L.-J. Heterostructures based on two-dimensional layered materials and their potential applications. Mater. Today 2016, 19 (6), 322– 335, DOI: 10.1016/j.mattod.2015.11.00334https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhvVyqu73E&md5=c32cd974de826059f4c93ceb193bcc07Heterostructures based on two-dimensional layered materials and their potential applicationsLi, Ming-Yang; Chen, Chang-Hsiao; Shi, Yumeng; Li, Lain-JongMaterials Today (Oxford, United Kingdom) (2016), 19 (6), 322-335CODEN: MTOUAN; ISSN:1369-7021. (Elsevier Ltd.)The development of two-dimensional (2D) layered materials is driven by fundamental interest and their potential applications. Atomically thin 2D materials provide a wide range of basic building blocks with unique elec., optical, and thermal properties which do not exist in their bulk counterparts. The van der Waals interlayer interaction enables the possibility to exfoliate and reassemble different 2D materials into arbitrarily and vertically stacked heterostructures. Recently developed vapor phase growth of 2D materials further paves the way of directly synthesizing vertical and lateral heterojunctions. This review provides insights into the layered 2D heterostructures, with a concise introduction to preparative approaches for 2D materials and heterostructures. These unique 2D heterostructures have abundant implications for many potential applications.
- 35Zhao, A. L.; Li, H.; Hu, X. J.; Wang, C.; Zhang, H.; Lu, J. G.; Ruan, S. C.; Zeng, Y. J. Review of 2D group VA material-based heterostructures. J. Phys. D: Appl. Phys. 2020, 53 (29), 293002, DOI: 10.1088/1361-6463/ab810c35https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXhsFSrtr%252FK&md5=a41bbbf559154c140dde7a26f3c63c2cReview of 2D group VA material-based heterostructuresZhao, Ailun; Li, Hui; Hu, Xuejuan; Wang, Cong; Zhang, Han; Lu, Jianguo; Ruan, Shuangchen; Zeng, Yu-JiaJournal of Physics D: Applied Physics (2020), 53 (29), 293002CODEN: JPAPBE; ISSN:0022-3727. (IOP Publishing Ltd.)A review. The isolation of black phosphorus (BP) and extraordinary performance of the BP field-effect transistor have led to BP offering remarkable properties in the two-dimensional (2D) family. Along with BP, other group VA element materials have been demonstrated to possess superior electronic and optical properties. However, numerous challenges remain to be overcome in their practical applications. Heterostructures play a vital role in modern semiconductors, and 2D group VA materials provide the opportunity to fabricate novel heterostructures that are combined by van der Waals forces. Previous theor. and exptl. studies have indicated that constructing a heterostructure is a promising strategy to conquer the obstacles and boost the development of 2D group VA materials. In this paper, we summarize the recent progress in 2D group VA material-based heterostructures. Firstly, the crystal structures and fundamental elec. properties of 2D group VA materials are introduced. Thereafter, various heterostructures based on group VA materials are discussed. Finally, conclusions and the outlook on emerging group VA heterostructures are presented.
- 36Wang, Z. F.; Yao, M.-Y.; Ming, W.; Miao, L.; Zhu, F.; Liu, C.; Gao, C. L.; Qian, D.; Jia, J.-F.; Liu, F. Creation of helical Dirac fermions by interfacing two gapped systems of ordinary fermions. Nat. Commun. 2013, 4 (1), 1384, DOI: 10.1038/ncomms238736https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADC%252BC3szhvF2nsw%253D%253D&md5=043cf56996e81863decff65d8c5d01c9Creation of helical Dirac fermions by interfacing two gapped systems of ordinary fermionsWang Z F; Yao Meng-Yu; Ming Wenmei; Miao Lin; Zhu Fengfeng; Liu Canhua; Gao C L; Qian Dong; Jia Jin-Feng; Liu FengNature communications (2013), 4 (), 1384 ISSN:.Topological insulators are a unique class of materials characterized by a Dirac cone state of helical Dirac fermions in the middle of a bulk gap. When the thickness of a three-dimensional topological insulator is reduced, however, the interaction between opposing surface states opens a gap that removes the helical Dirac cone, converting the material back to a normal system of ordinary fermions. Here we demonstrate, using density function theory calculations and experiments, that it is possible to create helical Dirac fermion state by interfacing two gapped films-a single bilayer Bi grown on a single quintuple layer Bi(2)Se(3) or Bi(2)Te(3). These extrinsic helical Dirac fermions emerge in predominantly Bi bilayer states, which are created by a giant Rashba effect with a coupling constant of ~4 eV·ÅA due to interfacial charge transfer. Our results suggest that this approach is a promising means to engineer topological insulator states on non-metallic surfaces.
- 37Yeom, H. W.; Kim, S. H.; Shin, W. J.; Jin, K.-H.; Park, J.; Kim, T.-H.; Kim, J. S.; Ishikawa, H.; Sakamoto, K.; Jhi, S.-H. Transforming a surface state of a topological insulator by a Bi capping layer. Phys. Rev. B: Condens. Matter Mater. Phys. 2014, 90 (23), 235401, DOI: 10.1103/PhysRevB.90.23540137https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXislWntbc%253D&md5=fba76577c174f741dd9c33b02243a97aTransforming a surface state of a topological insulator by a Bi capping layerYeom, Han Woong; Kim, Sung Hwan; Shin, Woo Jong; Jin, Kyung-Hwan; Park, Joonbum; Kim, Tae-Hwan; Kim, Jun Sung; Ishikawa, Hirotaka; Sakamoto, Kazuyuki; Jhi, Seung-HoonPhysical Review B: Condensed Matter and Materials Physics (2014), 90 (23), 235401/1-235401/5, 5 pp.CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)We introduce a distinct approach to engineer a topol. protected surface state of a topol. insulator. By covering the surface of a topol. insulator, Bi2Te2Se, with a Bi monolayer film, the original surface state is completely removed and three new spin helical surface states, originating from the Bi film, emerge with different dispersion and spin polarization, through a strong electron hybridization. These new states play the role of topol. surface states keeping the bulk topol. nature intact. This mechanism provides a way to create various different types of topol. protected electron channels on top of a single topol. insulator, possibly with tailored properties for various applications.
- 38Jin, K.-H.; Yeom, H. W.; Jhi, S.-H. Band structure engineering of topological insulator heterojunctions. Phys. Rev. B: Condens. Matter Mater. Phys. 2016, 93 (7), 075308, DOI: 10.1103/PhysRevB.93.075308There is no corresponding record for this reference.
Supporting Information
Supporting Information
The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.nanolett.1c02811.
Computational and experimental methods, electron/hole doping dependent stability, the SOC splitting of the valence and conduction bands, the distribution of the Berry curvature gradient, Berry curvature with the opposite polarization, band structures of the Bi(110) monolayer under an out-of-plane electric field, the conventional Rashba and out-of-plane Rashba model, large-scale topography, surface characterization via XPD, interface effect on band structures, charge density difference of the Bi/NbSe2 interface, origin of the linear dispersion, and the BCD for Bi/NbSe2 heterosystem (PDF)
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