近日，美国康奈尔大学的Kin Fai Mak&Kaifei Kang及其研究团队取得新进展。经过不懈努力，他们揭示莫尔MoTe₂中分数量子自旋霍尔效应的证据。相关研究成果已于2024年3月20日在国际权威学术期刊《自然》上发表。

该研究团队报道了在2.1°扭曲双层MoTe2中观测到分数QSH绝缘子的输运证据，这支持了自旋-S_z守恒和平自旋对比的陈能带理论。当莫尔价带的填充因子ν为3时，每条边的电导达到3/2G₀，而反常霍尔电导率为零。这种状态可能是偶数分母3/2分数陈绝缘子的时间反演对称对。此外，在ν分别为2、4和6时，研究团队观察到单个、两个和三个QSH绝缘子，对应的每条边电导分别是G₀、2G₀和3G₀。这项研究为在高度可调谐的莫尔材料中实现时间反演对称非阿贝尔任意子及其他新奇拓扑相提供了可能性，开辟了新的研究途径。

据悉，量子自旋霍尔(QSH)绝缘体是一种二维电子材料，具有与普通绝缘体相似的体带隙，但具有相反手性的拓扑保护边缘模式对。迄今为止，实验研究表明，仅有整数QSH绝缘体在每边呈现反向传播的上自旋和下自旋，从而实现了量子化电导G₀=e²/h（其中e为电子电荷，h为普朗克常数）。

附：英文原文

Title: Evidence of the fractional quantum spin Hall effect in moiré MoTe₂

Author: Kang, Kaifei, Shen, Bowen, Qiu, Yichen, Zeng, Yihang, Xia, Zhengchao, Watanabe, Kenji, Taniguchi, Takashi, Shan, Jie, Mak, Kin Fai

Issue&Volume: 2024-03-20

Abstract: Quantum spin Hall (QSH) insulators are two-dimensional electronic materials that have a bulk band gap similar to an ordinary insulator but have topologically protected pairs of edge modes of opposite chiralities. So far, experimental studies have found only integer QSH insulators with counter-propagating up-spins and down-spins at each edge leading to a quantized conductance G₀=e²/h (with e and h denoting the electron charge and Planck’s constant, respectively). Here we report transport evidence of a fractional QSH insulator in 2.1° twisted bilayer MoTe₂, which supports spin-S_z conservation and flat spin-contrasting Chern bands. At filling factor ν=3 of the moiré valence bands, each edge contributes a conductance 3/2G0 with zero anomalous Hall conductivity. The state is probably a time-reversal pair of the even-denominator 3/2-fractional Chern insulators. Furthermore, at ν=2, 4 and 6, we observe a single, double and triple QSH insulator with each edge contributing a conductance G₀, 2G₀ and 3G₀, respectively. Our results open up the possibility of realizing time-reversal symmetric non-abelian anyons and other unexpected topological phases in highly tunable moiré materials.

DOI: 10.1038/s41586-024-07214-5

Source: https://www.nature.com/articles/s41586-024-07214-5