TY - JOUR
T1 - Competing Zero-Field Chern Insulators in Superconducting Twisted Bilayer Graphene
AU - Stepanov, Petr
AU - Xie, Ming
AU - Taniguchi, Takashi
AU - Watanabe, Kenji
AU - Lu, Xiaobo
AU - Macdonald, Allan H.
AU - Bernevig, B. Andrei
AU - Efetov, Dmitri K.
N1 - Funding Information:
We are grateful for fruitful discussions with Frank H. L. Koppens and Ashvin Vishwanath. D. K. E. acknowledges support from the Ministry of Economy and Competitiveness of Spain through the “Severo Ochoa” program for Centres of Excellence in R&D (SE5-0522), Fundació Privada Cellex, Fundació Privada Mir-Puig, the Generalitat de Catalunya through the CERCA program, funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (Grant No. 852927) and the La Caixa Foundation. B. A. B. was supported by the DOE Grant No. DE-SC0016239, the Schmidt Fund for Innovative Research, Simons Investigator Grant No. 404513, the Packard Foundation, the Gordon and Betty Moore Foundation through Grant No. GBMF8685 toward the Princeton theory program, and a Guggenheim Fellowship from the John Simon Guggenheim Memorial Foundation. Further support was provided by the NSF-EAGER No. DMR 1643312, NSF-MRSEC No. DMR-1420541 and DMR-2011750, ONR No. N00014-20-1-2303, Gordon and Betty Moore Foundation through Grant No. GBMF8685 toward the Princeton theory program, BSF Israel U.S. foundation No. 2018226, and the Princeton Global Network Funds. A. H. M. and M. X. were supported by DOE Grant No. DE-FG02-02ER45958 and Welch Foundation Grant No. F1473. P. S. acknowledges support from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie Grant No. 754510.
Publisher Copyright:
© 2021 American Physical Society.
PY - 2021/11/5
Y1 - 2021/11/5
N2 - The discovery of magic angle twisted bilayer graphene has unveiled a rich variety of superconducting, magnetic, and topologically nontrivial phases. Here, we show that the zero-field states at odd integer filling factors in h-BN nonaligned devices are consistent with symmetry broken Chern insulators, as is evidenced by the observation of the anomalous Hall effect near moiré cell filling factor ν=+1. The corresponding Chern insulator has a Chern number C=±1 and a relatively high Curie temperature of Tc≈4.5 K. In a perpendicular magnetic field above B>0.5 T we observe a transition of the ν=+1 Chern insulator from Chern number C=±1 to C=3, characterized by a quantized Hall plateau with Ryx=h/3e2. These observations demonstrate that interaction-induced symmetry breaking leads to zero-field ground states that include almost degenerate and closely competing Chern insulators, and that states with larger Chern numbers couple most strongly to the B field. In addition, the device reveals strong superconducting phases with critical temperatures of up to Tc≈3.5 K. By providing the first demonstration of a system that allows gate-induced transitions between magnetic and superconducting phases, our observations mark a major milestone in the creation of a new generation of quantum electronics.
AB - The discovery of magic angle twisted bilayer graphene has unveiled a rich variety of superconducting, magnetic, and topologically nontrivial phases. Here, we show that the zero-field states at odd integer filling factors in h-BN nonaligned devices are consistent with symmetry broken Chern insulators, as is evidenced by the observation of the anomalous Hall effect near moiré cell filling factor ν=+1. The corresponding Chern insulator has a Chern number C=±1 and a relatively high Curie temperature of Tc≈4.5 K. In a perpendicular magnetic field above B>0.5 T we observe a transition of the ν=+1 Chern insulator from Chern number C=±1 to C=3, characterized by a quantized Hall plateau with Ryx=h/3e2. These observations demonstrate that interaction-induced symmetry breaking leads to zero-field ground states that include almost degenerate and closely competing Chern insulators, and that states with larger Chern numbers couple most strongly to the B field. In addition, the device reveals strong superconducting phases with critical temperatures of up to Tc≈3.5 K. By providing the first demonstration of a system that allows gate-induced transitions between magnetic and superconducting phases, our observations mark a major milestone in the creation of a new generation of quantum electronics.
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U2 - 10.1103/PhysRevLett.127.197701
DO - 10.1103/PhysRevLett.127.197701
M3 - Article
C2 - 34797145
AN - SCOPUS:85119423829
SN - 0031-9007
VL - 127
JO - Physical review letters
JF - Physical review letters
IS - 19
M1 - A63
ER -