Evidence of the fractional quantum spin Hall effect in moiré MoTe2

Kaifei Kang (), Bowen Shen, Yichen Qiu, Yihang Zeng, Zhengchao Xia, Kenji Watanabe, Takashi Taniguchi, Jie Shan () and Kin Fai Mak ()
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Kaifei Kang: Cornell University
Bowen Shen: Cornell University
Yichen Qiu: Cornell University
Yihang Zeng: Cornell University
Zhengchao Xia: Cornell University
Kenji Watanabe: National Institute for Materials Science
Takashi Taniguchi: National Institute for Materials Science
Jie Shan: Cornell University
Kin Fai Mak: Cornell University

Nature, 2024, vol. 628, issue 8008, 522-526

Abstract: 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 chiralities1–6. 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)7–14. Here we report transport evidence of a fractional QSH insulator in 2.1° twisted bilayer MoTe2, which supports spin-Sz conservation and flat spin-contrasting Chern bands15,16. At filling factor ν = 3 of the moiré valence bands, each edge contributes a conductance $$\frac{3}{2}{G}_{0}$$ 3 2 G 0 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 materials17–19.

Date: 2024
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DOI: 10.1038/s41586-024-07214-5

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