Excitonic density wave and spin-valley superfluid in bilayer transition metal dichalcogenide
Abstract
Artificial moiré superlattices in 2d van der Waals heterostructures are a new venue for realizing and controlling correlated electronic phenomena. Recently, twisted bilayer WSe2 emerged as a new robust moiré system hosting a correlated insulator at moiré half-filling over a range of twist angle. In this work, we present a theory of this insulating state as an excitonic density wave due to intervalley electron–hole pairing. We show that exciton condensation is strongly enhanced by a van Hove singularity near the Fermi level. Our theory explains the remarkable sensitivity of the insulating gap to the vertical electric field. In contrast, the gap is weakly reduced by a perpendicular magnetic field, with quadratic dependence at low field. The different responses to electric and magnetic field can be understood in terms of pair-breaking versus non-pair-breaking effects in a BCS analog of the system. We further predict superfluid spin transport in this electrical insulator, which can be detected by optical spin injection and spatial-temporal imaging.
- Authors:
-
[1];
- Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Dept. of Physics; Pennsylvania State Univ., University Park, PA (United States). Dept. of Physics
- Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Dept. of Physics
- Publication Date:
- Research Org.:
- Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
- Sponsoring Org.:
- USDOE Office of Science (SC), Basic Energy Sciences (BES)
- OSTI Identifier:
- 1816462
- Grant/Contract Number:
- SC0018945
- Resource Type:
- Accepted Manuscript
- Journal Name:
- Nature Communications
- Additional Journal Information:
- Journal Volume: 12; Journal Issue: 1; Journal ID: ISSN 2041-1723
- Publisher:
- Nature Publishing Group
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS
Citation Formats
Bi, Zhen, and Fu, Liang. Excitonic density wave and spin-valley superfluid in bilayer transition metal dichalcogenide. United States: N. p., 2021.
Web. doi:10.1038/s41467-020-20802-z.
Bi, Zhen, & Fu, Liang. Excitonic density wave and spin-valley superfluid in bilayer transition metal dichalcogenide. United States. https://doi.org/10.1038/s41467-020-20802-z
Bi, Zhen, and Fu, Liang. Thu .
"Excitonic density wave and spin-valley superfluid in bilayer transition metal dichalcogenide". United States. https://doi.org/10.1038/s41467-020-20802-z. https://www.osti.gov/servlets/purl/1816462.
@article{osti_1816462,
title = {Excitonic density wave and spin-valley superfluid in bilayer transition metal dichalcogenide},
author = {Bi, Zhen and Fu, Liang},
abstractNote = {Artificial moiré superlattices in 2d van der Waals heterostructures are a new venue for realizing and controlling correlated electronic phenomena. Recently, twisted bilayer WSe2 emerged as a new robust moiré system hosting a correlated insulator at moiré half-filling over a range of twist angle. In this work, we present a theory of this insulating state as an excitonic density wave due to intervalley electron–hole pairing. We show that exciton condensation is strongly enhanced by a van Hove singularity near the Fermi level. Our theory explains the remarkable sensitivity of the insulating gap to the vertical electric field. In contrast, the gap is weakly reduced by a perpendicular magnetic field, with quadratic dependence at low field. The different responses to electric and magnetic field can be understood in terms of pair-breaking versus non-pair-breaking effects in a BCS analog of the system. We further predict superfluid spin transport in this electrical insulator, which can be detected by optical spin injection and spatial-temporal imaging.},
doi = {10.1038/s41467-020-20802-z},
journal = {Nature Communications},
number = 1,
volume = 12,
place = {United States},
year = {Thu Jan 28 00:00:00 EST 2021},
month = {Thu Jan 28 00:00:00 EST 2021}
}
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