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

The unusual properties of superconductivity in magic-angle twisted bilayer graphene (MATBG) have sparked considerable research interest<sup>1-13</sup>. However, despite the dedication of intensive experimental efforts and the proposal of several possible pairing mechanisms<sup>14-24</sup>, 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 substrate<sup>11</sup>. 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.

Authors

Institutions

Publication Details

Journal
Nature
Published
2024-12-11
DOI
https://doi.org/10.1038/s41586-024-08227-w
Citations
49
Primary Topic
Graphene research and applications
Type
article
Field-Weighted Citation Impact
5.74

Funders

Controls
|||
ALL TIME
JAN
FEB
MAR
APR
MAY
JUN
JUL
AUG
SEP
OCT
article

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

Hanbo Xiao, Ryan L. Lee, Ali Yazdani, Dillon Wong et al.
49 citations
Nature
Graphene research and applications
5.74
article

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

Hanbo Xiao, Ryan L. Lee, Ali Yazdani, Dillon Wong, Bogdan Andrei Bernevig, Eli Rotenberg, Ding Pei, Shuhan Ding, Myungchul Oh, Takashi Taniguchi, Shanmei He, Kenji Watanabe, Lin He, Chris M. Jozwiak, Zhongkai Liu, Haoran Yan, Aaron Bostwick, Ding Pan, Xi Dai, Wangqian Miao, Jianpeng Liu, Kevin P. Nuckolls, Chen-Yue Hao, Yao Wang, Qiao Li, Yulin Chen, Shihao Zhang, Han Gao, Chu Li, Cheng Chen, Yiwei Li, Xu Han, Cheng Peng, Chao‐Xing Liu
article en
49 citations

Abstract

The unusual properties of superconductivity in magic-angle twisted bilayer graphene (MATBG) have sparked considerable research interest<sup>1-13</sup>. However, despite the dedication of intensive experimental efforts and the proposal of several possible pairing mechanisms<sup>14-24</sup>, 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 substrate<sup>11</sup>. 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.

NatureVol. 636(8042)
Ikerbasque (ES), Pohang University of Science and Technology (KR), Pennsylvania State University (US), Lawrence Berkeley National Laboratory (US), Emory University (US), University of California, Santa Barbara (US), Hong Kong University of Science and Technology (HK), Princeton University (US), National Institute for Materials Science (JP), Beijing Normal University (CN), ShanghaiTech University (CN), Wuhan University (CN), University of Oxford (GB), Donostia International Physics Center (ES), Massachusetts Institute of Technology (US), Clemson University (US)
National Science Foundation, U.S. Department of Energy, Gordon and Betty Moore Foundation, University of Pennsylvania, Pennsylvania State University, Princeton Center for Complex Materials, European Commission, National Natural Science Foundation of China, Hong Kong University of Science and Technology, ShanghaiTech University, Office of Science, Materials Research Science and Engineering Center, Harvard University, Multidisciplinary University Research Initiative, Office of Naval Research, Division of Materials Research, Kavli Institute for Theoretical Physics, University of California, Santa Barbara, Basic Energy Sciences, Army Research Office
Openalex Percentile: Top 1%
Graphene research and applications
5.74
DOIOpen Access PDFOpenAlex
AI Navigator

Ask Laika to Summarize, Analyze, and Connect papers live on the map.

Summarize Papers & Methodologies

Extract key findings, datasets, and comparative methods across publications.

Benchmark Rankings & Visual Analytics

Rank top research institutions, authors, funders, topics, and journals by Field-Weighted Citation Impact (FWCI) and paper volume with instant charts.

Connect Distant Disciplines

Bridge topological clusters on the map to find hidden collaborative intersections.