Interaction-induced metallic state in graphene on hexagonal boron nitride

Abstract

The Coulomb interaction is widely known to enhance the effective mass of interacting particles and therefore tends to favor a localized state at commensurate filling. Here, we will show that, in contrast to this consensus, in a van der Waals heterostructure consisting of graphene and hexagon boron nitride (h-BN), the onsite Coulomb repulsion will at first destroy the localized state. This is due to the fact that the onsite Coulomb repulsion tends to suppress the asymmetry between neighboring carbons induced by h-BN substrate. We corroborate this surprising phenomenon by solving a tightbinding model with onsite Coulomb repulsion treated within coherent potential approximation, where hopping parameters are derived from density functional theory calculations based on the graphene/h-BN heterostructure. Our results indicate that both gapless and gapped states observed experimentally in graphene/h-BN heterostructures can be understood after a realistic value of the onsite Coulomb repulsion as well as different interlayer distances are taken into account. Finally, we propose ways to enhance the gapped state which is essential for potential application of graphene to next-generation electronics. Furthermore, we argue that band gap suppressed by many-body effect should happen in other van der Waals heterostructures.

Antiferromagnetic spin valve based on a heterostructure of two-dimensional hexagonal crystals

“…1(a). A similar conclusion was given by the theoretical calculation of the Hubbard model with dynamical mean field theory [78,79]. In contrast, for the Hamiltonian H 0 + H AF + H U , the gap is enlarged, as shown in Fig.…”

Laser Shock Tuning Dynamic Interlayer Coupling in Graphene–Boron Nitride Moiré Superlattices

“…As shown in Fig. 1(c), in the Gr/BN/Gr heterolayer, all three layer bear large lattice strain with obvious difference, both intra-and inter-layer lattice mismatch is modulated distinctly, which is the origin of coupling modulation [17][18][19] .…”

“…To evaluate the lattice structure evolution after laser shock, first-principle calculations are conducted. As shown in Figure c, in the Gr/BN/Gr heterolayer, all three layers bear a large lattice strain with obvious differences, both intralayer and interlayer lattice mismatches are modulated distinctly, which is the origin of the coupling modulation. − Since the interlayer couplings are of van der Waal nature , even a weak change in the interlayer distance will have a dramatic impact on interlayer couplings.…”

“…After laser shocking, the enhancement of out-of-plane atomic coupling and the reduction of interlayer distance will make the total energy of the heterostructures increased. To release the total energy, it is required to soften the 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 in-plane interactions with expanded in-plane lattice, so the covalent bonds in the two sublattices becomes weaker, leading to the red-shift of G peak [17][18][19] . According to Raman measurements, the results of graphene, BN atomic sheet, and Gr/BN/Gr heterostructures with/without laser shocking are shown in Fig 2(c), respectively.…”

Have mysterious topological valley currents been observed in graphene superlattices?

“…We also note that the debate overviewed above is confined to quantum transport phenomena of noninteracting quasiparticles. Additional quantum many-body effects, such as due to on-site Coulomb interaction [26] which could close the gap of van der Waals heterostructure including graphene/hBN [27], are beyond either the standard Kubo formula used in [1,8,10,13] or the Landauer-Büttiker formula used in [13]. Their inclusion into a quantum transport formalism capable to model multiterminal devices would require major new theoretical advances [28].…”