Quantum Hall effect （QHE）, as a class of quantum phenomena that occur in macroscopic scale, is one of the most important topics in condensed matter physics. It has long been expected that QHE may occur without Landa...Quantum Hall effect （QHE）, as a class of quantum phenomena that occur in macroscopic scale, is one of the most important topics in condensed matter physics. It has long been expected that QHE may occur without Landau levels so that neither external magnetic field nor high sample mobility is required for its study and application, Such a QHE free of Landau levels, can appear in topological insulators （TIs） with ferromagnetism as the quantized version of the anomalous Hall effect, i.e., quantum anomalous Hall （QAH） effect. Here we review our recent work on experimental realization of the QAH effect in magnetically doped TIs. With molecular beam epitaxy, we prepare thin films of Cr-doped （Bi,Sb）2Te3 TIs with well- controlled chemical potential and long-range ferromagnetic order that can survive the insulating phase. In such thin films, we eventually observed the quantization of the Hall resistance at h/e2 at zero field, accompanied by a considerable drop in the longitudinal resistance. Under a strong magnetic field, the longitudinal resistance vanishes, whereas the Hall resistance remains at the quantized value. The realization of the QAH effect provides a foundation for many other novel quantum phenomena predicted in TIs, and opens a route to practical applications of quantum Hall physics in low-power-consumption electronics.展开更多
We review our theoretical advances in tunable topological quantum states in three- and two- dimensional materials with strong spin-orbital couplings. In three-dimensional systems, we propose a new tunable topological ...We review our theoretical advances in tunable topological quantum states in three- and two- dimensional materials with strong spin-orbital couplings. In three-dimensional systems, we propose a new tunable topological insulator, bismuth-based skutterudites in which topological insulating states can be induced by external strains. The orbitals involved in the topological band-inversion process are the d- and p-orbitals, unlike typical topological insulators such as Bi=Sea and BiTeI, where only the p-orbitals are involved in the band-inversion process. Owing to the presence of large d-electronic states, the electronic interaction in our proposed topological insulator is much stronger than that in other conventional topological insulators. In two-dimensional systems, we in- vestigated 3d-transition-metal-doped silicene. Using both an analytical model and first-principles Wannier interpolation, we demonstrate that silicene decorated with certain 3d transition metals such as vanadium can sustain a stable quantum anomalous Hall effect. We also predict that the quantum valley Hall effect and electrically tunable topological states could be realized in certain transition-metal-doped silicenes where the energy band inversion occurs. These findings provide realistic materials in which topological states could be arbitrarily controlled.展开更多
基金supported by the National Natural Science Foundation of China (11964024 and 12364038)the “Grassland Talents” Project of Inner Mongolia Autonomous Region (12000-12102613)the Young Science and Technology Talents Cultivation Project of Inner Mongolia University (21200-5223708)。
基金supported by the National Natural Science Foundation of China(12274112)the Overseas Scientists Sponsorship Program of Hebei Province(C20210330)+2 种基金the S&T Program of Hebei(215676146H and 225676163GH)the State Key Laboratory of Reliability and Intelligence of Electrical Equipment of Hebei University of Technology(EERI_PI2020009)the Australian Research Council(DP190100150 and DP210101436)。
基金supported by the National Natural Science Foundation of China (Grant Nos. 11174343 and 11134008)the National Basic Research Program of China(Grant Nos. 2013CB921702 and 2009CB929400)the Knowledge Innovation Program of the Chinese Academy of Sciences
文摘Quantum Hall effect （QHE）, as a class of quantum phenomena that occur in macroscopic scale, is one of the most important topics in condensed matter physics. It has long been expected that QHE may occur without Landau levels so that neither external magnetic field nor high sample mobility is required for its study and application, Such a QHE free of Landau levels, can appear in topological insulators （TIs） with ferromagnetism as the quantized version of the anomalous Hall effect, i.e., quantum anomalous Hall （QAH） effect. Here we review our recent work on experimental realization of the QAH effect in magnetically doped TIs. With molecular beam epitaxy, we prepare thin films of Cr-doped （Bi,Sb）2Te3 TIs with well- controlled chemical potential and long-range ferromagnetic order that can survive the insulating phase. In such thin films, we eventually observed the quantization of the Hall resistance at h/e2 at zero field, accompanied by a considerable drop in the longitudinal resistance. Under a strong magnetic field, the longitudinal resistance vanishes, whereas the Hall resistance remains at the quantized value. The realization of the QAH effect provides a foundation for many other novel quantum phenomena predicted in TIs, and opens a route to practical applications of quantum Hall physics in low-power-consumption electronics.
基金Acknowledgements We acknowledge helpful discussions with H. M. Weng, L. F. Liu, X. X. Wu., C. C. Liu, and J. J. Zhou. This work was supported by the National Key Basic Research Special Foundation of China under grant Nos. 2011CB921502 and 2012CB821305, the National Natural Science Foundation of China under grant Nos. 61227902, 61378017, and 11434015, SKLQO- QOD under grant No. KF201403, SPRPCAS under grant No. XDB01020300. The numerical calculations are performed on the Shenteng supercomputer at CNIC-CAS and on the Dawning clus- ter at IOP-CAS.
文摘We review our theoretical advances in tunable topological quantum states in three- and two- dimensional materials with strong spin-orbital couplings. In three-dimensional systems, we propose a new tunable topological insulator, bismuth-based skutterudites in which topological insulating states can be induced by external strains. The orbitals involved in the topological band-inversion process are the d- and p-orbitals, unlike typical topological insulators such as Bi=Sea and BiTeI, where only the p-orbitals are involved in the band-inversion process. Owing to the presence of large d-electronic states, the electronic interaction in our proposed topological insulator is much stronger than that in other conventional topological insulators. In two-dimensional systems, we in- vestigated 3d-transition-metal-doped silicene. Using both an analytical model and first-principles Wannier interpolation, we demonstrate that silicene decorated with certain 3d transition metals such as vanadium can sustain a stable quantum anomalous Hall effect. We also predict that the quantum valley Hall effect and electrically tunable topological states could be realized in certain transition-metal-doped silicenes where the energy band inversion occurs. These findings provide realistic materials in which topological states could be arbitrarily controlled.
