Doubled Moir\'{e} Flat Bands in Double-twisted Few Layer Graphite

TL;DR

This paper investigates double-twisted few-layer graphite, revealing it hosts doubled moiré flat bands at the Fermi level, leading to stronger electronic correlations than twisted bilayer graphene, with tunable degeneracy and topological properties.

Contribution

It demonstrates that double-twisted few-layer graphite can host doubled moiré flat bands, a novel finding that enhances the understanding of moiré systems and their correlation effects.

Findings

Doubled moiré flat bands at the Fermi level in DTFLG.

Enhanced density of states compared to TBG.

Degeneracy can be lifted by electric field, with nonzero valley Chern number.

Abstract

We study the electronic structure of a double-twisted few layer graphite (DTFLG), which consists of three few layer graphite (FLG), i.e. ABA-stacked graphene multilayer, stacked with two twist angles. We consider two categories of DTFLG, alternately twisted case and chirally twisted one, according to the rotation direction of the two twist angles. We show that, once the middle FLG of DTFLG is not thinner than trilayer, both kinds of DTFLG can remarkably host two pairs of degenerate moir\'{e} flat bands (MFBs) at $E_f$, twice that of the magic angle twisted bilayer graphene (TBG). The doubled MFBs of DTFLG lead to doubled DOS at $E_f$, which implies much stronger correlation effects than the TBG. The degeneracy of MFBs can be lifted by a perpendicular electric field, and the isolated MFBs have nonzero valley Chern number. We also reveal the peculiar wave function patterns of the MFBs in the DTFLG. Our results establish a new family of moir\'{e} systems that have the much larger DOS at $E_f$, and thus possible much stronger correlation effects.