Moiré excitons in biased twisted bilayer graphene under pressure

Abstract

Using the tight-binding model, we report a gap opening in the energy spectrum of a twisted bilayer graphene under the application of pressure, that can be further amplified by the presence of a perpendicular bias voltage. The valley edges are located along the $K\text{−}\mathrm{\Gamma }$ path of the superlattice Brillouin zone, with the band gap reaching values up to 200 meV in the single-particle picture. Employing the formalism of the semiconductor Bloch equations, we observe an enhancement of the band gap due to the electron-electron interaction, with a renormalization of the band gap of about 160 meV. From the solution of the corresponding Bethe-Salpeter equation, we show that this system supports highly anisotropic bright excitons whose electrons and holes are strongly hybridized between the adjacent layers.