Doubled Moiré Flat Bands in Double-twisted Few Layer Graphite

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 moiré 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 moiré systems that have the much larger DOS at E f , and thus possible much stronger correlation effects.

Moire Band Structures of the Double twisted Few Layer Graphene

“…We first discuss the continuum model of a general DT-FLG, which was given in Ref. 39. Here, we give a short introduction about the continuum Hamiltonian.…”

“…where Here, I ij is a matrix with only one nonzero matrix element 39 . For instance, in a (X+Y+Z)-DTFLG, the only nonzero matrix element of I 12 is I 12 (X, 1) = 1.…”

“…unconventional superconductivity, based on moiré flat bands. However, the moiré band structures of other double twisted moiré materials have been paid little attention so far [39][40][41][42][43] , though the band structures of the ATTLG and CTTLG were theoretically predicted two years ago.…”

“…In contrast, the CTTLG is a perfect metal gapless at all energies 33 . Meanwhile, using different kinds of vdW layers also can give rise to various moiré band structures 39,[44][45][46] . In double twisted TLG, the three vdW layers are all monolayer graphene (MLG).…”

“…Actually, if graphene multilayers are used as building blocks to construct double twisted moiré heterostructure, namely double twisted few layer graphene (DTFLG), more interesting moiré flat band structures can be achieved. For example, our recent work 39 predicts that, once a ABA-stacked TLG is used to replace the the middle vdW layer of the double twisted TLG, it can produce doubled moiré flat bands, i.e., four degenerate moiré flat bands at E f . It directly doubles the density of states (DOS) at E f , and thus will greatly enhance the correlation effects.…”