Spectroscopy of a tunable moiré system with a correlated and topological flat band

Liu, Xiaomeng; Chiu, Cheng-Li; Lee, Jong Yeon; Farahi, Gelareh; Watanabe, Kenji; Taniguchi, Takashi; Vishwanath, Ashvin; Yazdani, Ali

doi:10.1038/s41467-021-23031-0

Spectroscopy of a tunable moiré system with a correlated and topological flat band

Journal Article · Wed May 12 04:00:00 EDT 2021 · Nature Communications

DOI:https://doi.org/10.1038/s41467-021-23031-0· OSTI ID:1782754

; Chiu, Cheng-Li; Lee, Jong Yeon; Farahi, Gelareh; ; ; Vishwanath, Ashvin;

Abstract

Moiré superlattices created by the twisted stacking of two-dimensional crystals can host electronic bands with flat energy dispersion in which enhanced interactions promote correlated electron states. The twisted double bilayer graphene (TDBG), where two Bernal bilayer graphene are stacked with a twist angle, is such a moiré system with tunable flat bands. Here, we use gate-tuned scanning tunneling spectroscopy to directly demonstrate the tunability of the band structure of TDBG with an electric field and to show spectroscopic signatures of electronic correlations and topology for its flat band. Our spectroscopic experiments are in agreement with a continuum model of TDBG band structure and reveal signatures of a correlated insulator gap at partial filling of its isolated flat band. The topological properties of this flat band are probed with the application of a magnetic field, which leads to valley polarization and the splitting of Chern bands with a large effective g-factor.

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Sponsoring Organization:: USDOE

Grant/Contract Number:: NONE; FG02-07ER46419

OSTI ID:: 1782754

Alternate ID(s):: OSTI ID: 1816549
OSTI ID: 1839078

Journal Information:: Nature Communications, Journal Name: Nature Communications Journal Issue: 1 Vol. 12; ISSN 2041-1723

Publisher:: Nature Publishing GroupCopyright Statement

Country of Publication:: United Kingdom

Language:: English

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