Electrical band flattening, valley flux, and superconductivity in twisted trilayer graphene

Abstract

Twisted graphene multilayers have been demonstrated to yield a versatile playground to engineer controllable electronic states. Here, by combining first-principles calculations and low-energy models, we demonstrate that twisted graphene trilayers provide a tunable system where Van Hove singularities can be controlled electrically. In particular, it is shown that besides the band flattening, bulk valley currents appear, which can be quenched by local chemical dopants. We finally show that in the presence of electronic interactions, a nonuniform superfluid density emerges whose nonuniformity gives rise to spectroscopic signatures in dispersive higher-energy bands. Our results put forward twisted trilayers as a tunable van der Waals heterostructure displaying electrically controllable flat bands and bulk valley currents.

Emulating Heavy Fermions in Twisted Trilayer Graphene

“…1(c) for V ¼ 0. We highlight the emergence of flat bands, similar to the ones observed in twisted bilayer graphene at the magic angle, coexisting with dispersive modes [25][26][27][28]38]. Interestingly, when applying an interlayer bias, this twisted system develops even flatter bands, as shown in Fig.…”

“…More complex twisted graphene multilayers, such as twisted bi-bilayers [7,10] and trilayers [21][22][23], have provided additional platforms to realize similar physics as twisted graphene bilayers. The possibility of tuning several twist angles in multilayer graphene [24][25][26][27][28] suggests that these systems may realize correlated states of matter beyond the ones already observed in twisted bilayers.…”

“…This finding proposes a new perspective on the global phase diagram for heavy fermions [33,34]. While a precise first-principles estimate of all the couplings is challenging [25], the exact system's parameters can be inferred from experiments looking at the evolution of the tunneling spectra as a function of temperature and magnetic fields in different directions. In particular, below the coherence temperature, Fano-like resonances appear and the characteristic parameters of the line shape can be extracted and identified with model parameters such as the hybridization between localized and delocalized states [86][87][88][89][90].…”

Moire Band Structures of the Double twisted Few Layer Graphene

“…The discovery of unconventional superconductivity and broken-symmetry states in alternating twisted trilayer graphene (ATTLG) has drawn great research interest very recently [1][2][3][4][5][6] . It is of special importance because that the ATTLG gives a second definite example of moiré superconductor in addition to the celebrated twisted bilayer graphene (TBG) [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] .…”

Magic angle and plasmon mode engineering in twisted trilayer graphene with pressure

“…Twisted bilayer graphene (tBG) with a "magic angle" ( 1.1 • ) has gained extensive attention since the discovery of gate-tunable unconventional superconductivity and strongly correlated insulating phases, which are due to the presence of ultraflat bands near the Fermi level [1,2]. Recently, experimental and theoretical investigations have been shown that twisted trilayer graphene (tTLG) has a better tunability of its superconducting phases than the twisted bilayer graphene, which makes it a good platform to study the correlated properties [3][4][5][6][7][8][9][10]. Plenty of degrees of freedom, for instance, the twist angle, stacking configurations, external electric field, and interlayer separation, are available to tune the electronic properties of the tTLG.…”