Pressure induced gap modulation and topological transitions in twisted bilayer and double bilayer graphene

Abstract

We study the electronic and topological properties of fully relaxed twisted bilayer (TBG) and double bilayer (TDBG) graphene under perpendicular pressure. An approach has been proposed to obtain the equilibrium in-plane structural deformation and out-of-plane corrugation in moiré superlattices under pressure. We find that the in-plane relaxation becomes much stronger under higher pressure, while the corrugation height in each layer is maintained. The comparison between band structures of relaxed and rigid structures demonstrates that not only the gaps on the electron and hole sides (${\Delta }_e$ and ${\Delta }_h$) are significantly underestimated without relaxation but also the detailed dispersions of the middle bands of rigid structures are rather different from those of relaxed systems. ${\Delta }_e$ and ${\Delta }_h$ in TBG reach maximum values around critical pressures with narrowest middle bands. Topological transitions occur in TDBG under pressure with the middle valence and conduction bands in one valley touching and their Chern numbers transferred to each other. The pressure can also tune the gap at the neutrality point of TDBG, which becomes closed for a pressure range and reopened under higher pressure. The behavior of electronic structure of supertlattices under pressure is sensitive to the twist angle $\theta$ with the critical pressures generally increase with $\theta$.

11 pages, 7 figures

References in corpus (10)

• The electronic properties of graphene
• Flat Bands in Slightly Twisted Bilayer Graphene
• Continuum Model of the Twisted Bilayer
• Lattice relaxation and energy band modulation in twisted bilayer graphenes
• Numerical studies of confined states in rotated bilayers of graphene
• Flatbands in twisted double bilayer graphene
• Band structure and topological property of twisted double bilayer graphenes
• The crucial role of atomic corrugation on the flat bands and energy gaps of twisted bilayer graphene at the "magic angle" $\theta \sim 1.08^{\circ }$
• Continuum models for twisted bilayer graphene: the effects of lattice deformation and hopping parameter
• Structure of twisted and buckled bilayer graphene

Cited by in corpus (3)

• Tailoring the band structure of twisted double bilayer graphene with pressure
• Symmetry breaking in the double moiré superlattices of relaxed twisted bilayer graphene on hexagonal boron nitride
• Electronic properties of twisted multilayer graphene