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Evidence of the fractional quantum spin Hall effect in moiré MoTe2

Cornell Affiliated Author(s)


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


Quantum spin Hall (QSH) insulators are two-dimensional electronic materials that have a bulk band gap like an ordinary insulator but have topologically protected pairs of edge modes of opposite chiralities. To date, 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=e^2/h. Here we report transport evidence of a fractional QSH insulator in 2.1-degree-twisted bilayer MoTe2, which supports spin-Sz conservation and flat spin-contrasting Chern bands. At filling factor v = 3 of the moiré valence bands, each edge contributes a conductance 3/2 G0 with zero anomalous Hall conductivity. The state is likely a time-reversal pair of the even-denominator 3/2-fractional Chern insulators. Further, at v = 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.

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Group (Lab)

Jie Shan Group
Kin Fai Mak Group

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