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Twisted symmetric trilayer graphene: Single-particle and many-body Hamiltonians and hidden nonlocal symmetries of trilayer moiré systems with and without displacement field

Dumitru Călugăru, Fang Xie, Zhi-Da Song, Biao Lian, Nicolas Regnault, and B. Andrei Bernevig
Phys. Rev. B 103, 195411 – Published 10 May 2021

Abstract

We derive the Hamiltonian for trilayer moiré systems with the Coulomb interaction projected onto the bands near the charge neutrality point. Motivated by the latest experimental results, we focus on the twisted symmetric trilayer graphene (TSTG) with a mirror symmetry with respect to the middle layer. We provide a full symmetry analysis of the noninteracting Hamiltonian with a perpendicular displacement field coupling the band structure made otherwise of the twisted bilayer graphene (TBG) and the high-velocity Dirac fermions, and we identify a hidden nonlocal symmetry of the problem. In the presence of this displacement field, we construct an approximate single-particle model, akin to the tripod model for TBG, capturing the essence of noninteracting TSTG. We also derive more quantitative perturbation schemes for the low-energy physics of TSTG with displacement field, obtaining the corresponding eigenstates. This allows us to obtain the Coulomb interaction Hamiltonian projected in the active band TSTG wave functions and derive the full many-body Hamiltonian of the system. We also provide an efficient parametrization of the interacting Hamiltonian. Finally, we show that the discrete symmetries at the single-particle level promote the U2×U2 spin-valley symmetry to enlarged symmetry groups of the interacting problem under different limits. The interacting part of the Hamiltonian exhibits a large U4×U4×U4×U4 symmetry in the chiral limit. Moreover, by identifying a symmetry which we dub spatial many-body charge conjugation, we show that the physics of TSTG is symmetric around charge neutrality.

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  • Received 25 February 2021
  • Accepted 12 April 2021

DOI:https://doi.org/10.1103/PhysRevB.103.195411

©2021 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Dumitru Călugăru1,*, Fang Xie1, Zhi-Da Song1, Biao Lian1, Nicolas Regnault1,2,*, and B. Andrei Bernevig1,*

  • 1Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
  • 2Laboratoire de Physique de l'Ecole normale superieure, ENS, Université PSL, CNRS, Sorbonne Université, Université Paris-Diderot, Sorbonne Paris Cité, Paris, France

  • *These authors contributed equally to this work.

See Also

Twisted symmetric trilayer graphene. II. Projected Hartree-Fock study

Fang Xie, Nicolas Regnault, Dumitru Călugăru, B. Andrei Bernevig, and Biao Lian
Phys. Rev. B 104, 115167 (2021)

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Vol. 103, Iss. 19 — 15 May 2021

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