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Title: Valley magnetism, nematicity, and density wave orders in twisted bilayer graphene

Abstract

We analyze density wave and Pomeranchuk orders in twisted bilayer graphene. This complements our earlier analysis of the pairing instabilities. We assume that near half filling of either conduction or valence band, the Fermi level is close to Van Hove points, where the density of states diverges, and study potential instabilities in the particle-hole channel within a patch model with two valley degrees of freedom. The hexagonal symmetry of twisted bilayer graphene allows for either six or twelve Van Hove points. We consider both cases and find the same two leading candidates for particle-hole order. One is an SU(2)-breaking spin state with ferromagnetism within a valley. A subleading intervalley hopping induces antiferromagnetism between the valleys. The same state has also been obtained in strong-coupling approaches, indicating that this order is robust. Here, the other is a mixed state with 120° complex spin order and orthogonal complex charge order. In addition, we find a weaker but still attractive interaction in nematic channels, and discuss the type of a nematic order.

Authors:
 [1]; ORCiD logo [2]; ORCiD logo [1]
  1. Univ. of Minnesota, Minneapolis, MN (United States)
  2. Univ. of Minnesota, Minneapolis, MN (United States); Brookhaven National Lab. (BNL), Upton, NY (United States)
Publication Date:
Research Org.:
Brookhaven National Lab. (BNL), Upton, NY (United States); Univ. of Minnesota, Minneapolis, MN (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES); Humboldt Foundation
OSTI Identifier:
1670668
Alternate Identifier(s):
OSTI ID: 1660737
Report Number(s):
BNL-219920-2020-JAAM
Journal ID: ISSN 2469-9950
Grant/Contract Number:  
SC0012704; SC0014402
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 102; Journal Issue: 12; Journal ID: ISSN 2469-9950
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; magnetism; twisted bilayer graphene; exotic phases of matter; order parameters; phase diagrams

Citation Formats

Chichinadze, Dmitry V., Classen, Laura, and Chubukov, Andrey V. Valley magnetism, nematicity, and density wave orders in twisted bilayer graphene. United States: N. p., 2020. Web. doi:10.1103/physrevb.102.125120.
Chichinadze, Dmitry V., Classen, Laura, & Chubukov, Andrey V. Valley magnetism, nematicity, and density wave orders in twisted bilayer graphene. United States. doi:10.1103/physrevb.102.125120.
Chichinadze, Dmitry V., Classen, Laura, and Chubukov, Andrey V. Mon . "Valley magnetism, nematicity, and density wave orders in twisted bilayer graphene". United States. doi:10.1103/physrevb.102.125120.
@article{osti_1670668,
title = {Valley magnetism, nematicity, and density wave orders in twisted bilayer graphene},
author = {Chichinadze, Dmitry V. and Classen, Laura and Chubukov, Andrey V.},
abstractNote = {We analyze density wave and Pomeranchuk orders in twisted bilayer graphene. This complements our earlier analysis of the pairing instabilities. We assume that near half filling of either conduction or valence band, the Fermi level is close to Van Hove points, where the density of states diverges, and study potential instabilities in the particle-hole channel within a patch model with two valley degrees of freedom. The hexagonal symmetry of twisted bilayer graphene allows for either six or twelve Van Hove points. We consider both cases and find the same two leading candidates for particle-hole order. One is an SU(2)-breaking spin state with ferromagnetism within a valley. A subleading intervalley hopping induces antiferromagnetism between the valleys. The same state has also been obtained in strong-coupling approaches, indicating that this order is robust. Here, the other is a mixed state with 120° complex spin order and orthogonal complex charge order. In addition, we find a weaker but still attractive interaction in nematic channels, and discuss the type of a nematic order.},
doi = {10.1103/physrevb.102.125120},
journal = {Physical Review B},
issn = {2469-9950},
number = 12,
volume = 102,
place = {United States},
year = {2020},
month = {9}
}

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