Quantum valley Hall states in low-buckled counterparts of graphene bilayer
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arXiv
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| Main Authors: | , , , , , |
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| Format: | Preprint |
| Published: |
2024
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| _version_ | 1866909502605885440 |
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| author | Shen, Yu-Hao Zheng, Jun-Ding Tong, Wen-Yi Bao, Zhi-Qiang Wan, Xian-Gang Duan, Chun-Gang |
| author_facet | Shen, Yu-Hao Zheng, Jun-Ding Tong, Wen-Yi Bao, Zhi-Qiang Wan, Xian-Gang Duan, Chun-Gang |
| contents | With low-buckled structure for each layer in graphene bilayer system, there breaks inversion symmetry (P-symmetry) for one stacking when both A and B sublattices in top layer are aligned with those in bottom layer. In consideration of spin-orbit coupling (SOC), there opens nontrivial topological gap in each monolayer system to achieve quantum spin Hall effect (QSHE). As long as time-reversal symmetry (T-symmetry) is preserved the gapless edge states is robust in each individual layer even for the bilayer absent of PT symmetry. Based on this platform and through tight-binding (TB) model calculations we find it becomes a typical system that can exhibit quantum valley Hall effect (QVHE) when introduced a layer-resolved Rashba SOC that leads to band inversion at each K valley in the hexagonal Brillion zone (BZ). The topological transition comes from that the valley Chern number Cv = CK - CK' switches from 0 to 2, which characterizes the nontrivial QVHE phase transited from two coupled Z2 topological insulators. We also point that the layer-resolved Rashba SOC can be introduced equivalently by twisting two van der Waals touched layers. And through TB calculations, it is shown that the K bands inverts in its corresponding mini BZ when the two layers twisted by a small angle. Our findings advance potential applications for the devices design in topological valleytronics and twistronics. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2403_13277 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Quantum valley Hall states in low-buckled counterparts of graphene bilayer Shen, Yu-Hao Zheng, Jun-Ding Tong, Wen-Yi Bao, Zhi-Qiang Wan, Xian-Gang Duan, Chun-Gang Mesoscale and Nanoscale Physics Materials Science With low-buckled structure for each layer in graphene bilayer system, there breaks inversion symmetry (P-symmetry) for one stacking when both A and B sublattices in top layer are aligned with those in bottom layer. In consideration of spin-orbit coupling (SOC), there opens nontrivial topological gap in each monolayer system to achieve quantum spin Hall effect (QSHE). As long as time-reversal symmetry (T-symmetry) is preserved the gapless edge states is robust in each individual layer even for the bilayer absent of PT symmetry. Based on this platform and through tight-binding (TB) model calculations we find it becomes a typical system that can exhibit quantum valley Hall effect (QVHE) when introduced a layer-resolved Rashba SOC that leads to band inversion at each K valley in the hexagonal Brillion zone (BZ). The topological transition comes from that the valley Chern number Cv = CK - CK' switches from 0 to 2, which characterizes the nontrivial QVHE phase transited from two coupled Z2 topological insulators. We also point that the layer-resolved Rashba SOC can be introduced equivalently by twisting two van der Waals touched layers. And through TB calculations, it is shown that the K bands inverts in its corresponding mini BZ when the two layers twisted by a small angle. Our findings advance potential applications for the devices design in topological valleytronics and twistronics. |
| title | Quantum valley Hall states in low-buckled counterparts of graphene bilayer |
| topic | Mesoscale and Nanoscale Physics Materials Science |
| url | https://arxiv.org/abs/2403.13277 |