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arXiv · 2504.11530

Probing Quantum Anomalous Hall States in Twisted Bilayer WSe2 via Attractive Polaron Spectroscopy

Beini Gao·Mahdi Ghafariasl·Mahmoud Jalali Mehrabad·Tsung-Sheng Huang·Lifu Zhang·Deric Session·Pranshoo Upadhyay·Rundong Ma·Ghadah Alshalan·Daniel Gustavo Suárez Forero·Supratik Sarkar·Suji Park·Houk Jang·Kenji Watanabe·Takashi Taniguchi·Ming Xie·You Zhou·Mohammad Hafezi
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Abstract

Moir\'e superlattices in semiconductors exhibit a rich variety of interaction-induced topological states, including quantum anomalous Hall (QAH) effects. A recent study hinted that twisted WSe2 homobilayer (tWSe2) could host a QAH state but lacked direct evidence of ferromagnetism, a key hallmark of this phase. Here, we report the first direct evidence of QAH states in tWSe2 with spontaneous ferromagnetism. Specifically, we employ polarization-resolved attractive polaron spectroscopy on a dual-gated, 2 degree tWSe2 and observe direct signatures of spontaneous time-reversal symmetry breaking at hole filling \nu = 1. Together with a Chern number measurement via Streda formula analysis, we identify this magnetized state as a topological state, characterized by C = 1. Furthermore, we demonstrate that these topological and magnetic properties are tunable via a finite displacement field, between a QAH ferromagnetic state and an antiferromagnetic state. Our findings position tWSe2 as a highly versatile, stable, and optically addressable platform for investigating topological order and strong correlations in two-dimensional landscapes.

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Beini Gao, Mahdi Ghafariasl, Mahmoud Jalali Mehrabad, Tsung-Sheng Huang, Lifu Zhang, Deric Session, Pranshoo Upadhyay, Rundong Ma, Ghadah Alshalan, Daniel Gustavo Suárez Forero, Supratik Sarkar, Suji Park, Houk Jang, Kenji Watanabe, Takashi Taniguchi, Ming Xie, You Zhou, Mohammad Hafezi. 2025-04-15. Probing Quantum Anomalous Hall States in Twisted Bilayer WSe2 via Attractive Polaron Spectroscopy. https://doi.org/10.1103/259w-bpxx

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