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

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.

Authors:

Liu, Xiaomeng ;

• Search DOE PAGES for author "Liu, Xiaomeng"
• Search DOE PAGES for ORCID "0000-0002-0039-7090"

Chiu, Cheng-Li; Lee, Jong Yeon; Farahi, Gelareh; Watanabe, Kenji ;

• Search DOE PAGES for author "Watanabe, Kenji"
• Search DOE PAGES for ORCID "0000-0003-3701-8119"

Taniguchi, Takashi ;

• Search DOE PAGES for author "Taniguchi, Takashi"
• Search DOE PAGES for ORCID "0000-0002-1467-3105"

Vishwanath, Ashvin; Yazdani, Ali

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

Publication Date:

Wed May 12 00:00:00 EDT 2021

Research Org.:

Princeton Univ., NJ (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES); Gordon and Betty Moore Foundation; National Science Foundation (NSF); JSPS KAKENHI; CREST; MEXT

OSTI Identifier:

1782754

Alternate Identifier(s):

OSTI ID: 1816549; OSTI ID: 1839078

Grant/Contract Number:  

FG02-07ER46419; GBMF4530; GBMF9469; DMR-1420541; DMR-1904442; DMR-2011750; JPMXP0112101001; JP20H00354; JPMJCR15F3

Resource Type:

Published Article

Journal Name:

Nature Communications

Additional Journal Information:

Journal Name: Nature Communications Journal Volume: 12 Journal Issue: 1; Journal ID: ISSN 2041-1723

Publisher:

Nature Publishing Group

Country of Publication:

United Kingdom

Language:

English

Subject:

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; electronic properties and devices; electronic properties and materials; topological matter; 36 MATERIALS SCIENCE; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY