Kang Kaifei, Qiu Yichen, Watanabe Kenji, Taniguchi Takashi, Shan Jie, Mak Kin Fai
School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, United States.
Department of Physics, Cornell University, Ithaca, New York 14853, United States.
Nano Lett. 2024 Nov 20;24(46):14901-14907. doi: 10.1021/acs.nanolett.4c05308. Epub 2024 Nov 6.
Quantum spin Hall (QSH) insulators are topologically protected phases of matter in two dimensions that can support a pair of helical edge states surrounding an insulating bulk. A higher (even) number of helical edge state pairs is usually not possible in real materials because spin mixing would gap out the edge states. Here, we report experimental evidence for a QSH phase with one and two pairs of helical edge states in twisted bilayer WSe at Moiré hole filling factor ν = 2 and 4, respectively. We observe nearly quantized (within 10%) resistance plateaus of and large nonlocal transport at ν = 2 and 4 while the bulk is insulating. The resistance is independent of the out-of-plane magnetic field and increases under an in-plane magnetic field. The results agree with quantum transport of helical edge states in a material with high spin Chern bands protected by Ising spin conservation symmetry.
量子自旋霍尔（QSH）绝缘体是二维拓扑保护的物相，其能在绝缘体态周围支持一对螺旋边缘态。在实际材料中，通常不可能存在更多（偶数）对螺旋边缘态，因为自旋混合会使边缘态出现能隙。在此，我们报告了在扭曲双层WSe₂中，分别在莫尔填充因子ν = 2和4时具有一对和两对螺旋边缘态的QSH相的实验证据。我们观察到在ν = 2和4时，体态绝缘的情况下，电阻有近乎量子化（在10%以内）的 平台以及大的非局域输运。电阻与面外磁场无关，而在面内磁场下增大。这些结果与具有由伊辛自旋守恒对称性保护的高自旋陈数能带的材料中螺旋边缘态的量子输运相一致。
