• Letter
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Topological piezoelectric response in moiré graphene systems

Ran Peng and Jianpeng Liu
Phys. Rev. Research 4, L032006 – Published 11 July 2022
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Abstract

We theoretically study the piezoelectric effects in moirè graphene systems. Since the strain couples to the electrons in the system as an effective vector field, which has opposite signs for the K and K valleys of graphene, its effects on the two valleys with opposite Chern numbers do not cancel out, but adds up. As a result, some components of the piezoelectric tensor (PET) in these systems, which typically have nontrivial topology in their flat bands, are nearly quantized in terms of the valley Chern numbers. The quantization of the PET is topologically protected by valley U(1) symmetry of the system. Such a conclusion is verified by numerical calculations of the in-plane piezoelectric response of hBN-aligned twisted bilayer graphene (TBG), twisted bilayer-monolayer graphene (TBMG), and twisted double bilayer graphene (TDBG) systems using both continuum model and atomistic tight-binding model. We propose that such nearly quantized piezoelectric response may serve as a direct experimental probe for the valley Chern numbers of the flat bands in moiré graphene systems.

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  • Received 26 September 2021
  • Accepted 25 May 2022

DOI:https://doi.org/10.1103/PhysRevResearch.4.L032006

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Published by the American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Ran Peng

  • School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China

Jianpeng Liu*

  • School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China and ShanghaiTech Laboratory for Topological Physics, ShanghaiTech University, Shanghai 201210, China

  • *liujp@shanghaitech.edu.cn

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Issue

Vol. 4, Iss. 3 — July - September 2022

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