Correlation-Induced Insulating Topological Phases at Charge Neutrality in Twisted Bilayer Graphene

Twisted bilayer graphene (TBG) provides a unique framework to elucidate the interplay between strong correlations and topological phenomena in two-dimensional systems. The existence of multiple electronic degrees of freedom—charge, spin, and valley—gives rise to a plethora of possible ordered states...

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Autores principales:	Yuan Da Liao, Jian Kang, Clara N. Breiø, Xiao Yan Xu, Han-Qing Wu, Brian M. Andersen, Rafael M. Fernandes, Zi Yang Meng
Formato:	article
Lenguaje:	EN
Publicado:	American Physical Society 2021
Materias:	Physics QC1-999
Acceso en línea:	https://doaj.org/article/8b3a411639244fd2bf0e95b6d7194e26
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spelling	oai:doaj.org-article:8b3a411639244fd2bf0e95b6d7194e262021-12-02T13:27:27ZCorrelation-Induced Insulating Topological Phases at Charge Neutrality in Twisted Bilayer Graphene10.1103/PhysRevX.11.0110142160-3308https://doaj.org/article/8b3a411639244fd2bf0e95b6d7194e262021-01-01T00:00:00Zhttp://doi.org/10.1103/PhysRevX.11.011014http://doi.org/10.1103/PhysRevX.11.011014https://doaj.org/toc/2160-3308Twisted bilayer graphene (TBG) provides a unique framework to elucidate the interplay between strong correlations and topological phenomena in two-dimensional systems. The existence of multiple electronic degrees of freedom—charge, spin, and valley—gives rise to a plethora of possible ordered states and instabilities. Identifying which of them are realized in the regime of strong correlations is fundamental to shed light on the nature of the superconducting and correlated insulating states observed in the TBG experiments. Here, we use unbiased, sign-problem-free quantum Monte Carlo simulations to solve an effective interacting lattice model for TBG at charge neutrality. Besides the usual cluster Hubbard-like repulsion, this model also contains an assisted-hopping interaction that emerges due to the nontrivial topological properties of TBG. Such a nonlocal interaction fundamentally alters the phase diagram at charge neutrality, gapping the Dirac cones even for infinitesimally small interactions. As the interaction strength increases, a sequence of different correlated insulating phases emerge, including a quantum valley Hall state with topological edge states, an intervalley-coherent insulator, and a valence bond solid. The charge-neutrality correlated insulating phases discovered here provide the sought-after reference states needed for a comprehensive understanding of the insulating states at integer fillings and the proximate superconducting states of TBG.Yuan Da LiaoJian KangClara N. BreiøXiao Yan XuHan-Qing WuBrian M. AndersenRafael M. FernandesZi Yang MengAmerican Physical SocietyarticlePhysicsQC1-999ENPhysical Review X, Vol 11, Iss 1, p 011014 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Physics QC1-999
spellingShingle	Physics QC1-999 Yuan Da Liao Jian Kang Clara N. Breiø Xiao Yan Xu Han-Qing Wu Brian M. Andersen Rafael M. Fernandes Zi Yang Meng Correlation-Induced Insulating Topological Phases at Charge Neutrality in Twisted Bilayer Graphene
description	Twisted bilayer graphene (TBG) provides a unique framework to elucidate the interplay between strong correlations and topological phenomena in two-dimensional systems. The existence of multiple electronic degrees of freedom—charge, spin, and valley—gives rise to a plethora of possible ordered states and instabilities. Identifying which of them are realized in the regime of strong correlations is fundamental to shed light on the nature of the superconducting and correlated insulating states observed in the TBG experiments. Here, we use unbiased, sign-problem-free quantum Monte Carlo simulations to solve an effective interacting lattice model for TBG at charge neutrality. Besides the usual cluster Hubbard-like repulsion, this model also contains an assisted-hopping interaction that emerges due to the nontrivial topological properties of TBG. Such a nonlocal interaction fundamentally alters the phase diagram at charge neutrality, gapping the Dirac cones even for infinitesimally small interactions. As the interaction strength increases, a sequence of different correlated insulating phases emerge, including a quantum valley Hall state with topological edge states, an intervalley-coherent insulator, and a valence bond solid. The charge-neutrality correlated insulating phases discovered here provide the sought-after reference states needed for a comprehensive understanding of the insulating states at integer fillings and the proximate superconducting states of TBG.
format	article
author	Yuan Da Liao Jian Kang Clara N. Breiø Xiao Yan Xu Han-Qing Wu Brian M. Andersen Rafael M. Fernandes Zi Yang Meng
author_facet	Yuan Da Liao Jian Kang Clara N. Breiø Xiao Yan Xu Han-Qing Wu Brian M. Andersen Rafael M. Fernandes Zi Yang Meng
author_sort	Yuan Da Liao
title	Correlation-Induced Insulating Topological Phases at Charge Neutrality in Twisted Bilayer Graphene
title_short	Correlation-Induced Insulating Topological Phases at Charge Neutrality in Twisted Bilayer Graphene
title_full	Correlation-Induced Insulating Topological Phases at Charge Neutrality in Twisted Bilayer Graphene
title_fullStr	Correlation-Induced Insulating Topological Phases at Charge Neutrality in Twisted Bilayer Graphene
title_full_unstemmed	Correlation-Induced Insulating Topological Phases at Charge Neutrality in Twisted Bilayer Graphene
title_sort	correlation-induced insulating topological phases at charge neutrality in twisted bilayer graphene
publisher	American Physical Society
publishDate	2021
url	https://doaj.org/article/8b3a411639244fd2bf0e95b6d7194e26
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Correlation-Induced Insulating Topological Phases at Charge Neutrality in Twisted Bilayer Graphene

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