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Title: Emergence of flat-band magnetism and half-metallicity in twisted bilayer graphene

Abstract

Evidence of flat-band magnetism and half-metallicity in compressed twisted bilayer graphene is provided with first-principles calculations. In this article, we show that dynamic band-structure engineering in twisted bilayer graphene is possible by controlling the chemical composition with extrinsic doping, the interlayer coupling strength with pressure, and the magnetic ordering with external electric field. By varying the rotational order and reducing the interlayer separation, an unbalanced distribution of charge density results in the spontaneous apparition of localized magnetic moments without disrupting the structural integrity of the bilayer. Weak exchange correlation between magnetic moments is estimated in large unit cells. External electric field switches the local magnetic ordering from ferromagnetic to antiferromagnetic. Substitutional doping shifts the chemical potential of one spin distribution and leads to half-metallicity. Lastly, flakes of compressed twisted bilayer graphene exhibit spontaneous magnetization, demonstrating that correlation between magnetic moments is not a necessary condition for their formation.

Authors:
ORCiD logo [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1529544
Alternate Identifier(s):
OSTI ID: 1518502
Report Number(s):
LA-UR-19-21862
Journal ID: ISSN 2475-9953; PRMHAR
Grant/Contract Number:  
89233218CNA000001
Resource Type:
Accepted Manuscript
Journal Name:
Physical Review Materials
Additional Journal Information:
Journal Volume: 3; Journal Issue: 5; Journal ID: ISSN 2475-9953
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; Bilayer graphene; Magnetism; DFT

Citation Formats

Lopez-Bezanilla, Alejandro. Emergence of flat-band magnetism and half-metallicity in twisted bilayer graphene. United States: N. p., 2019. Web. doi:10.1103/PhysRevMaterials.3.054003.
Lopez-Bezanilla, Alejandro. Emergence of flat-band magnetism and half-metallicity in twisted bilayer graphene. United States. doi:10.1103/PhysRevMaterials.3.054003.
Lopez-Bezanilla, Alejandro. Tue . "Emergence of flat-band magnetism and half-metallicity in twisted bilayer graphene". United States. doi:10.1103/PhysRevMaterials.3.054003.
@article{osti_1529544,
title = {Emergence of flat-band magnetism and half-metallicity in twisted bilayer graphene},
author = {Lopez-Bezanilla, Alejandro},
abstractNote = {Evidence of flat-band magnetism and half-metallicity in compressed twisted bilayer graphene is provided with first-principles calculations. In this article, we show that dynamic band-structure engineering in twisted bilayer graphene is possible by controlling the chemical composition with extrinsic doping, the interlayer coupling strength with pressure, and the magnetic ordering with external electric field. By varying the rotational order and reducing the interlayer separation, an unbalanced distribution of charge density results in the spontaneous apparition of localized magnetic moments without disrupting the structural integrity of the bilayer. Weak exchange correlation between magnetic moments is estimated in large unit cells. External electric field switches the local magnetic ordering from ferromagnetic to antiferromagnetic. Substitutional doping shifts the chemical potential of one spin distribution and leads to half-metallicity. Lastly, flakes of compressed twisted bilayer graphene exhibit spontaneous magnetization, demonstrating that correlation between magnetic moments is not a necessary condition for their formation.},
doi = {10.1103/PhysRevMaterials.3.054003},
journal = {Physical Review Materials},
number = 5,
volume = 3,
place = {United States},
year = {2019},
month = {5}
}

Journal Article:
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This content will become publicly available on May 28, 2020
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