Lattice relaxation, mirror symmetry and magnetic field effects on ultraflat bands in twisted trilayer graphene

TL;DR

This paper investigates how lattice relaxation and magnetic fields influence ultraflat bands in twisted trilayer graphene, revealing the importance of relaxation effects and the potential for accessible Hofstadter butterfly spectra, making tTLG a versatile platform for correlated phenomena.

Contribution

It demonstrates the critical role of lattice relaxation in tTLG's electronic properties and shows that Hofstadter butterfly spectra can be observed at laboratory magnetic fields, unlike in bilayer graphene.

Findings

Lattice relaxations significantly alter the quasiparticle spectrum.

Hofstadter butterfly spectrum is accessible at laboratory magnetic fields.

tTLG offers more tunability for studying correlated phenomena.

Abstract

Twisted graphene multilayers exhibit strongly correlated insulating states and superconductivity due to the presence of ultraflat bands near the charge neutral point. In this paper, the response of ultraflat bands to lattice relaxation and a magnetic field in twisted trilayer graphene (tTLG) with different stacking arrangements is investigated by using a full tight-binding model. We show that lattice relaxations are indispensable for understanding the electronic properties of tTLG, in particular, of tTLG in the presence of mirror symmetry. Lattice relaxations renormalize the quasiparticle spectrum near the Fermi energy and change the localization of higher energy flat bands. Furthermore, different from the twisted bilayer graphene, the Hofstadter butterfly spectrum can be realized at laboratory accessible strengths of magnetic field. Our work verifies tTLG as a more tunable platform than the twisted bilayer graphene in strongly correlated phenomena.