Title: Cascade of electronic transitions in magic-angle twisted bilayer graphene

Abstract

Magic-angle twisted bilayer graphene exhibits a variety of electronic states, including correlated insulators, superconductors and topological phases. Understanding the microscopic mechanisms responsible for these phases requires determination of the interplay between electron–electron interactions and quantum degeneracy (the latter is due to spin and valley degrees of freedom). Signatures of strong electron–electron correlations have been observed at partial fillings of the flat electronic bands in recent spectroscopic measurements, and transport experiments have shown changes in the Landau level degeneracy at fillings corresponding to an integer number of electrons per moiré unit cell. However, the interplay between interaction effects and the degeneracy of the system is currently unclear. Here in this paper we report a cascade of transitions in the spectroscopic properties of magic-angle twisted bilayer graphene as a function of electron filling, determined using high-resolution scanning tunnelling microscopy. We find distinct changes in the chemical potential and a rearrangement of the low-energy excitations at each integer filling of the moiré flat bands. These spectroscopic features are a direct consequence of Coulomb interactions, which split the degenerate flat bands into Hubbard sub-bands. We find these interactions, the strength of which we can extract experimentally, to be surprisingly sensitive to the presence ofmore » a perpendicular magnetic field, which strongly modifies the spectroscopic transitions. The cascade of transitions that we report here characterizes the correlated high-temperature parent phase from which various insulating and superconducting ground-state phases emerge at low temperatures in magic-angle twisted bilayer graphene.« less

Authors:

Wong, Dillon  ^[1];

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• Search DOE PAGES for ORCID "0000-0002-4931-4188"

Nuckolls, Kevin P.  ^[1];

• Search DOE PAGES for author "Nuckolls, Kevin P."
• Search DOE PAGES for ORCID "0000-0002-1078-7113"

Oh, Myungchul  ^[1];

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• Search DOE PAGES for ORCID "0000-0003-0477-1390"

Lian, Biao ^[2]; Xie, Yonglong  ^[3];

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• Search DOE PAGES for ORCID "0000-0001-7656-6324"

Jeon, Sangjun  ^[4];

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• Search DOE PAGES for ORCID "0000-0002-3134-7838"

Watanabe, Kenji  ^[5];

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• Search DOE PAGES for ORCID "0000-0003-3701-8119"

Taniguchi, Takashi ^[5]; Bernevig, B. Andrei  ^[2];

• Search DOE PAGES for author "Bernevig, B. Andrei"
• Search DOE PAGES for ORCID "0000-0001-6337-4024"

Yazdani, Ali  ^[1]

• Search DOE PAGES for author "Yazdani, Ali"
• Search DOE PAGES for ORCID "0000-0003-4996-8904"

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+ Show Author Affiliations

1. Princeton Univ., NJ (United States). Joseph Henry Laboratories
2. Princeton Univ., NJ (United States). Princeton Center for Theoretical Science
3. Princeton Univ., NJ (United States). Joseph Henry Laboratories; Harvard Univ., Cambridge, MA (United States); Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
4. Princeton Univ., NJ (United States). Joseph Henry Laboratories; Chung-Ang Univ., Seoul (Korea, Republic of)
5. National Institute for Material Science, Tsukuba (Japan)

Publication Date:

Thu Jun 11 00:00:00 EDT 2020

Research Org.:

Princeton Univ., NJ (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES); Gordon and Betty Moore Foundation (GBMF); Princeton University; National Science Foundation (NSF)

OSTI Identifier:

1780896

Grant/Contract Number:  

FG02-07ER46419; SC0016239; DMR12-1643312

Resource Type:

Accepted Manuscript

Journal Name:

Nature (London)

Additional Journal Information:

Journal Name: Nature (London); Journal Volume: 582; Journal Issue: 7811; Journal ID: ISSN 0028-0836

Publisher:

Nature Publishing Group

Country of Publication:

United States

Language:

English

Subject:

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; electronic properties and materials surfaces; interfaces and thin films