Strong electron–phonon coupling in magic-angle twisted bilayer graphene

Cheng Chen, Kevin P. Nuckolls, Shuhan Ding, Wangqian Miao, Dillon Wong, Myungchul Oh, Ryan L. Lee, Shanmei He, Cheng Peng, Ding Pei, Yiwei Li, Chenyue Hao, Haoran Yan, Hanbo Xiao, Han Gao, Qiao Li, Shihao Zhang, Jianpeng Liu, Lin He, Kenji Watanabe, Takashi Taniguchi, Chris Jozwiak, Aaron Bostwick, Eli Rotenberg, Chu Li, Xu Han, Ding Pan, Zhongkai Liu, Xi Dai, Chaoxing Liu, B. Andrei Bernevig, Yao Wang (), Ali Yazdani and Yulin Chen ()
Additional contact information
Cheng Chen: ShanghaiTech University
Kevin P. Nuckolls: Princeton University
Shuhan Ding: Emory University
Wangqian Miao: University of California, Santa Barbara
Dillon Wong: Princeton University
Myungchul Oh: Princeton University
Ryan L. Lee: Princeton University
Shanmei He: University of Oxford
Cheng Peng: University of Oxford
Ding Pei: ShanghaiTech University
Yiwei Li: Wuhan University
Chenyue Hao: Beijing Normal University
Haoran Yan: Emory University
Hanbo Xiao: ShanghaiTech University
Han Gao: ShanghaiTech University
Qiao Li: ShanghaiTech University
Shihao Zhang: ShanghaiTech University
Jianpeng Liu: ShanghaiTech University
Lin He: Beijing Normal University
Kenji Watanabe: National Institute for Materials Science
Takashi Taniguchi: National Institute for Materials Science
Chris Jozwiak: Lawrence Berkeley National Laboratory
Aaron Bostwick: Lawrence Berkeley National Laboratory
Eli Rotenberg: Lawrence Berkeley National Laboratory
Chu Li: Hong Kong University of Science and Technology
Xu Han: Hong Kong University of Science and Technology
Ding Pan: Hong Kong University of Science and Technology
Zhongkai Liu: ShanghaiTech University
Xi Dai: Hong Kong University of Science and Technology
Chaoxing Liu: The Pennsylvania State University
B. Andrei Bernevig: Princeton University
Yao Wang: Emory University
Ali Yazdani: Princeton University
Yulin Chen: ShanghaiTech University

Nature, 2024, vol. 636, issue 8042, 342-347

Abstract: Abstract The unusual properties of superconductivity in magic-angle twisted bilayer graphene (MATBG) have sparked considerable research interest1–13. However, despite the dedication of intensive experimental efforts and the proposal of several possible pairing mechanisms14–24, the origin of its superconductivity remains elusive. Here, by utilizing angle-resolved photoemission spectroscopy with micrometre spatial resolution, we reveal flat-band replicas in superconducting MATBG, where MATBG is unaligned with its hexagonal boron nitride substrate11. These replicas show uniform energy spacing, approximately 150 ± 15 meV apart, indicative of strong electron–boson coupling. Strikingly, these replicas are absent in non-superconducting twisted bilayer graphene (TBG) systems, either when MATBG is aligned to hexagonal boron nitride or when TBG deviates from the magic angle. Calculations suggest that the formation of these flat-band replicas in superconducting MATBG are attributed to the strong coupling between flat-band electrons and an optical phonon mode at the graphene K point, facilitated by intervalley scattering. These findings, although they do not necessarily put electron–phonon coupling as the main driving force for the superconductivity in MATBG, unravel the electronic structure inherent in superconducting MATBG, thereby providing crucial information for understanding the unusual electronic landscape from which its superconductivity is derived.

Date: 2024
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DOI: 10.1038/s41586-024-08227-w

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