Hartree theory calculations of quasiparticle properties in twisted bilayer graphene
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Published version
Author(s)
Goodwin, Zachary
Vitale, Valerio
Liang, Xia
Mostofi, Arash A
Lischner, Johannes
Type
Journal Article
Abstract
A detailed understanding of interacting electrons in twisted bilayer graphene
(tBLG) near the magic angle is required to gain insights into the physical
origin of the observed broken symmetry phases including correlated insulator
states and superconductivity. Here, we present extensive atomistic Hartree
theory calculations of the electronic properties of tBLG in the (semi-)metallic
phase as function of doping and twist angle. Specifically, we calculate
quasiparticle properties, such as the band structure, density of states (DOS)
and local density of states (LDOS), which are directly accessible in
photoemission and tunnelling spectroscopy experiments. We find that
quasiparticle properties change significantly upon doping - an effect which is
not captured by tight-binding theory. In particular, we observe that the
partially occupied bands flatten significantly which enhances the density of
states at the Fermi level and explains the experimentally observed Fermi level
pinning. We predict a clear signature of this band flattening in the LDOS in
the AB/BA regions of tBLG which can be tested in scanning tunneling
experiments. We also study the dependence of quasiparticle properties on the
dielectric environment of tBLG and discover that these properties are
surprisingly robust as a consequence of the strong internal screening. Finally,
we present a simple analytical expression for the Hartree potential which
enables the determination of quasiparticle properties without the need for
self-consistent calculations.
(tBLG) near the magic angle is required to gain insights into the physical
origin of the observed broken symmetry phases including correlated insulator
states and superconductivity. Here, we present extensive atomistic Hartree
theory calculations of the electronic properties of tBLG in the (semi-)metallic
phase as function of doping and twist angle. Specifically, we calculate
quasiparticle properties, such as the band structure, density of states (DOS)
and local density of states (LDOS), which are directly accessible in
photoemission and tunnelling spectroscopy experiments. We find that
quasiparticle properties change significantly upon doping - an effect which is
not captured by tight-binding theory. In particular, we observe that the
partially occupied bands flatten significantly which enhances the density of
states at the Fermi level and explains the experimentally observed Fermi level
pinning. We predict a clear signature of this band flattening in the LDOS in
the AB/BA regions of tBLG which can be tested in scanning tunneling
experiments. We also study the dependence of quasiparticle properties on the
dielectric environment of tBLG and discover that these properties are
surprisingly robust as a consequence of the strong internal screening. Finally,
we present a simple analytical expression for the Hartree potential which
enables the determination of quasiparticle properties without the need for
self-consistent calculations.
Date Issued
2020-09-01
Date Acceptance
2020-06-23
Citation
Physical Review B: Condensed Matter and Materials Physics, 2020, 2 (3)
ISSN
1098-0121
Publisher
American Physical Society
Journal / Book Title
Physical Review B: Condensed Matter and Materials Physics
Volume
2
Issue
3
Copyright Statement
© 2020 The Author(s). Published by IOP Publishing Ltd. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
License URL
Sponsor
Engineering & Physical Science Research Council (EPSRC)
Engineering and Physical Sciences Research Council
Identifier
http://arxiv.org/abs/2004.14784v2
Grant Number
EP/S025324/1
EPSRC (EP/L015579/1)
Subjects
cond-mat.mes-hall
cond-mat.mes-hall
cond-mat.mtrl-sci
cond-mat.str-el
Publication Status
Published
Article Number
ARTN 034001
Date Publish Online
2020-08-03