Competing Zero-Field Chern Insulators in Superconducting Twisted Bilayer Graphene
Abstract
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 majormore »
- Authors:
-
[1];
[3];
[1]
- Barcelona Institute of Science and Technology (BIST) (Spain)
- Univ. of Texas, Austin, TX (United States)
- National Institute for Materials Science (NIMS), Tsukuba (Japan)
- Princeton Univ., NJ (United States)
- Publication Date:
- Research Org.:
- Univ. of Texas, Austin, TX (United States); Princeton Univ., NJ (United States)
- Sponsoring Org.:
- USDOE Office of Science (SC); European Research Council (ERC); Simons Foundation; Gordon and Betty Moore Foundation; National Science Foundation (NSF); Welch Foundation
- OSTI Identifier:
- 1980227
- Grant/Contract Number:
- FG02-02ER45958; SC0016239; 852927; 754510; 404513; GBMF8685; DMR-1643312; DMR-1420541; DMR-2011750; N00014-20-1-2303; F1473
- Resource Type:
- Accepted Manuscript
- Journal Name:
- Physical Review Letters
- Additional Journal Information:
- Journal Volume: 127; Journal Issue: 19; Journal ID: ISSN 0031-9007
- Publisher:
- American Physical Society (APS)
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Physics; magnetic order; topological phase transition
Citation Formats
Stepanov, Petr, Xie, Ming, Taniguchi, Takashi, Watanabe, Kenji, Lu, Xiaobo, MacDonald, Allan H., Bernevig, B. Andrei, and Efetov, Dmitri K. Competing Zero-Field Chern Insulators in Superconducting Twisted Bilayer Graphene. United States: N. p., 2021.
Web. doi:10.1103/physrevlett.127.197701.
Stepanov, Petr, Xie, Ming, Taniguchi, Takashi, Watanabe, Kenji, Lu, Xiaobo, MacDonald, Allan H., Bernevig, B. Andrei, & Efetov, Dmitri K. Competing Zero-Field Chern Insulators in Superconducting Twisted Bilayer Graphene. United States. https://doi.org/10.1103/physrevlett.127.197701
Stepanov, Petr, Xie, Ming, Taniguchi, Takashi, Watanabe, Kenji, Lu, Xiaobo, MacDonald, Allan H., Bernevig, B. Andrei, and Efetov, Dmitri K. Tue .
"Competing Zero-Field Chern Insulators in Superconducting Twisted Bilayer Graphene". United States. https://doi.org/10.1103/physrevlett.127.197701. https://www.osti.gov/servlets/purl/1980227.
@article{osti_1980227,
title = {Competing Zero-Field Chern Insulators in Superconducting Twisted Bilayer Graphene},
author = {Stepanov, Petr and Xie, Ming and Taniguchi, Takashi and Watanabe, Kenji and Lu, Xiaobo and MacDonald, Allan H. and Bernevig, B. Andrei and Efetov, Dmitri K.},
abstractNote = {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.},
doi = {10.1103/physrevlett.127.197701},
journal = {Physical Review Letters},
number = 19,
volume = 127,
place = {United States},
year = {Tue Nov 02 00:00:00 EDT 2021},
month = {Tue Nov 02 00:00:00 EDT 2021}
}
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