Analytical solution for the relaxed atomic configuration of twisted bilayer graphene including heterostrain

Fuente: arXiv
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Autores principales: Kang, Jian, Vafek, Oskar
Formato: Preprint
Publicado: 2025
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author Kang, Jian
Vafek, Oskar
author_facet Kang, Jian
Vafek, Oskar
contents Continuum atomic relaxation models for twisted bilayer graphene involve minimization of the sum of intralayer elastic energy and interlayer adhesion energy. The elastic energy favors a rigid twist i.e. no distortion in the twisted honeycomb lattices, while the adhesion energy favors Bernal stacking and breaking the relaxation into triangular AB and BA stacked domains. We compare the results of two relaxation models with the published Bragg interferometry data, finding good agreement with one of the models. We then provide a method for finding a highly accurate approximation to the solution of this model which holds above the twist angle of $\approx0.7^\circ$ and thus covers the first magic angle. We find closed form expressions in the absence, as well as in the presence, of external heterostrain. These expressions are not written as a Taylor series in the ratio of adhesion and elastic energy, because, as we show, the radius of convergence of such a series is too small to access the first magic angle.
format Preprint
id arxiv_https___arxiv_org_abs_2502_15154
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Analytical solution for the relaxed atomic configuration of twisted bilayer graphene including heterostrain
Kang, Jian
Vafek, Oskar
Strongly Correlated Electrons
Mesoscale and Nanoscale Physics
Continuum atomic relaxation models for twisted bilayer graphene involve minimization of the sum of intralayer elastic energy and interlayer adhesion energy. The elastic energy favors a rigid twist i.e. no distortion in the twisted honeycomb lattices, while the adhesion energy favors Bernal stacking and breaking the relaxation into triangular AB and BA stacked domains. We compare the results of two relaxation models with the published Bragg interferometry data, finding good agreement with one of the models. We then provide a method for finding a highly accurate approximation to the solution of this model which holds above the twist angle of $\approx0.7^\circ$ and thus covers the first magic angle. We find closed form expressions in the absence, as well as in the presence, of external heterostrain. These expressions are not written as a Taylor series in the ratio of adhesion and elastic energy, because, as we show, the radius of convergence of such a series is too small to access the first magic angle.
title Analytical solution for the relaxed atomic configuration of twisted bilayer graphene including heterostrain
topic Strongly Correlated Electrons
Mesoscale and Nanoscale Physics
url https://arxiv.org/abs/2502.15154