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Probing Quantum Anomalous Hall States in Twisted Bilayer WSe 2 via Attractive Polaron Spectroscopy

Gao, Beini [Univ. of Maryland, College Park, MD (United States). Joint Quantum Institute (JQI)] (ORCID:0000000245444962)·Ghafariasl, Mahdi [Univ. of Maryland, College Park, MD (United States). Joint Quantum Institute (JQI)] (ORCID:0000000194791533)·Mehrabad, Mahmoud Jalali [Univ. of Maryland, College Park, MD (United States). Joint Quantum Institute (JQI)] (ORCID:0000000298099998)·Huang, Tsung-Sheng [Univ. of Maryland, College Park, MD (United States). Joint Quantum Institute (JQI)] (ORCID:0000000241378988)·Zhang, Lifu [Univ. of Maryland, College Park, MD (United States)]·Session, Deric [Univ. of Maryland, College Park, MD (United States). Joint Quantum Institute (JQI)]·Upadhyay, Pranshoo [Univ. of Maryland, College Park, MD (United States). Joint Quantum Institute (JQI)]·Ma, Rundong [Univ. of Maryland, College Park, MD (United States)]·Alshalan, Ghadah [Univ. of Maryland, College Park, MD (United States). Joint Quantum Institute (JQI)] (ORCID:0000000254319426)·Suarez, Daniel [Univ. of Maryland, College Park, MD (United States). Joint Quantum Institute (JQI)] (ORCID:0000000227576320)·Sarkar, Supratik [Univ. of Maryland, College Park, MD (United States). Joint Quantum Institute (JQI)] (ORCID:0000000326452307)·Park, Suji [Brookhaven National Laboratory (BNL), Upton, NY (United States). Center for Functional Nanomaterials (CFN)] (ORCID:0000000222697705)·Jang, Houk [Brookhaven National Laboratory (BNL), Upton, NY (United States). Center for Functional Nanomaterials (CFN)] (ORCID:0000000272361134)·Watanabe, Kenji [National Institute for Materials Science (NIMS), Tsukuba (Japan)] (ORCID:0000000337018119)·Taniguchi, Takashi [National Institute for Materials Science (NIMS), Tsukuba (Japan)] (ORCID:0000000214673105)·Xie, Ming [Univ. of Maryland, College Park, MD (United States); Univ. of Texas at Dallas, Richardson, TX (United States)] (ORCID:0000000278367967)·Zhou, You [Univ. of Maryland, College Park, MD (United States)] (ORCID:000000029854545X)·Hafezi, Mohammad [Univ. of Maryland, College Park, MD (United States). Joint Quantum Institute (JQI)] (ORCID:0000000316794880)
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Abstract

Moiré superlattices in semiconductors exhibit a rich variety of interaction-induced topological states, including quantum anomalous Hall (QAH) effects. A recent study hinted that twisted WSe 2 homobilayer (tWSe 2 ) 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 tWSe 2 with spontaneous ferromagnetism. Specifically, we employ polarization-resolved attractive polaron spectroscopy on a dual-gated, 2° tWSe 2 and observe direct signatures of spontaneous time-reversal symmetry breaking at hole filling 𝜈 = 1. Together with a Chern number (𝐶) 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 tWSe 2 as a highly versatile, stable, and optically addressable platform for investigating topological order and strong correlations in two-dimensional landscapes.

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Gao, Beini [Univ. of Maryland, College Park, MD (United States). Joint Quantum Institute (JQI)] (ORCID:0000000245444962), Ghafariasl, Mahdi [Univ. of Maryland, College Park, MD (United States). Joint Quantum Institute (JQI)] (ORCID:0000000194791533), Mehrabad, Mahmoud Jalali [Univ. of Maryland, College Park, MD (United States). Joint Quantum Institute (JQI)] (ORCID:0000000298099998), Huang, Tsung-Sheng [Univ. of Maryland, College Park, MD (United States). Joint Quantum Institute (JQI)] (ORCID:0000000241378988), Zhang, Lifu [Univ. of Maryland, College Park, MD (United States)], Session, Deric [Univ. of Maryland, College Park, MD (United States). Joint Quantum Institute (JQI)], Upadhyay, Pranshoo [Univ. of Maryland, College Park, MD (United States). Joint Quantum Institute (JQI)], Ma, Rundong [Univ. of Maryland, College Park, MD (United States)], Alshalan, Ghadah [Univ. of Maryland, College Park, MD (United States). Joint Quantum Institute (JQI)] (ORCID:0000000254319426), Suarez, Daniel [Univ. of Maryland, College Park, MD (United States). Joint Quantum Institute (JQI)] (ORCID:0000000227576320), Sarkar, Supratik [Univ. of Maryland, College Park, MD (United States). Joint Quantum Institute (JQI)] (ORCID:0000000326452307), Park, Suji [Brookhaven National Laboratory (BNL), Upton, NY (United States). Center for Functional Nanomaterials (CFN)] (ORCID:0000000222697705), Jang, Houk [Brookhaven National Laboratory (BNL), Upton, NY (United States). Center for Functional Nanomaterials (CFN)] (ORCID:0000000272361134), Watanabe, Kenji [National Institute for Materials Science (NIMS), Tsukuba (Japan)] (ORCID:0000000337018119), Taniguchi, Takashi [National Institute for Materials Science (NIMS), Tsukuba (Japan)] (ORCID:0000000214673105), Xie, Ming [Univ. of Maryland, College Park, MD (United States); Univ. of Texas at Dallas, Richardson, TX (United States)] (ORCID:0000000278367967), Zhou, You [Univ. of Maryland, College Park, MD (United States)] (ORCID:000000029854545X), Hafezi, Mohammad [Univ. of Maryland, College Park, MD (United States). Joint Quantum Institute (JQI)] (ORCID:0000000316794880). 2026-05-18. Probing Quantum Anomalous Hall States in Twisted Bilayer WSe 2 via Attractive Polaron Spectroscopy. https://doi.org/10.1103/259w-bpxx

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