Dichotomy of Electron-Phonon Coupling in Graphene Moiré Flat Bands

Young Woo Choi, Hyoung Joon Choi

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12 Citations (Scopus)


Graphene moiré superlattices are outstanding platforms to study correlated electron physics and superconductivity with exceptional tunability. However, robust superconductivity has been measured only in magic-angle twisted bilayer graphene (MA-TBG) and magic-angle twisted trilayer graphene (MA-TTG). The absence of a superconducting phase in certain moiré flat bands raises a question on the superconducting mechanism. In this work, we investigate electronic structure and electron-phonon coupling in graphene moiré superlattices based on atomistic calculations. We show that electron-phonon coupling strength is dramatically different among graphene moiré flat bands. The total strength is very large () for MA-TBG and MA-TTG, both of which display robust superconductivity in experiments. However, is an order of magnitude smaller in twisted double bilayer graphene (TDBG) and twisted monolayer-bilayer graphene (TMBG) where superconductivity is reportedly rather weak or absent. We find that the Bernal-stacked layers in TDBG and TMBG induce sublattice polarization in the flat-band states, suppressing intersublattice electron-phonon matrix elements. We also obtain the nonadiabatic superconducting transition temperature that matches well with the experimental results. Our results clearly show a correlation between strong electron-phonon coupling and experimental observations of robust superconductivity.

Original languageEnglish
Article number167001
JournalPhysical review letters
Issue number16
Publication statusPublished - 2021 Oct 15

Bibliographical note

Funding Information:
National Research Foundation of Korea Korea Institute of Science and Technology Information

Funding Information:
This work was supported by NRF of Korea (Grants No. 2020R1A2C3013673 and No. 2017R1A5A1014862) and KISTI supercomputing center (Project No. KSC-2020-CRE-0335). Y. W. C. acknowledges support from NRF of Korea (Global Ph.D. Fellowship Program NRF-2017H1A2A1042152).

Publisher Copyright:
© 2021 American Physical Society.

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)


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