Moiré Flat Bands of Twisted Few-layer Graphite

Abstract

We report that the twisted few layer graphite (tFL-graphite) is a new family of moiré heterostructures (MHSs), which has richer and highly tunable moiré flat band structures entirely distinct from all the known MHSs. A tFL-graphite is composed of two few-layer graphite (Bernal stacked multilayer graphene), which are stacked on each other with a small twisted angle. The moiré band structure of the tFL-graphite strongly depends on the layer number of its composed two van der Waals layers. Near the magic angle, a tFL-graphite always has two nearly flat bands coexisting with a few pairs of narrowed dispersive (parabolic or linear) bands at the Fermi level, thus, enhances the DOS at EF . This coexistence property may also enhance the possible superconductivity as been demonstrated in other multiband superconductivity systems. Therefore, we expect strong multiband correlation effects in tFL-graphite. Meanwhile, a proper perpendicular electric field can induce several isolated nearly flat bands with nonzero valley Chern number in some simple tFL-graphites, indicating that tFL-graphite is also a novel topological flat band system.

Moire Band Structures of the Double twisted Few Layer Graphene

“…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).…”

Emergence of intrinsically isolated flat bands and their topology in fully relaxed twisted multi-layer graphene

“…The electronic structure of TMLG depends on the stacking orders of the FLGs and the twist angle (θ) 32,[36][37][38][39][40][41] . The flat bands around the Fermi level (E F ) of TMLG were found to be entangled with each other or with other dispersive bands by band crossings 32,[38][39][40][41] .…”

“…Most studies introduced external electric field to separate the flat bands so that their band topology becomes well defined, while the produced C is limited to small values 39,41 . For TMLG composed of chirally stacked FLGs, the flat valence and conduction bands in a valley can be separated from other bands and their total C were demonstrated to increase with the layer numbers of TMLG 32 .…”

Doubled Moiré Flat Bands in Double-twisted Few Layer Graphite

“…Actually, MFB is a general phenomenon of moiré heterostructures (MHSs). It exists in many other similar MHSs, such as twisted double bilayer graphene [12][13][14][15][16][17][18][19][20][21][22][23], twisted trilayer graphene [24][25][26][27][28][29][30][31][32], trilayer graphene on boron nitride [33][34][35], twisted few layer graphite [36,37], etc. Interestingly, the MFBs in some of these MHSs are topological nontrivial [12-15, 24, 38, 39], and topological phenomena, e.g.…”

“…The other is the (ABA+ABA)-type twisted FLG, which is a single twist MHS. Though it also has four bands near E f at the two inequivalent Dirac points of the moiré BZ, a single twist can only induce one pair of MFBs at zero energy as well [36]. Our calculations indicate that all the DTFLG with N ≥ 3, meeting these two requirements above, have two pairs of degenerate MFBs at the magic angle about 1.08 • , the magic angle of which is the same as that of TBG but different from that of the double twisted trilayer graphene (about 1.5 • ) [43].…”