Tunable Excitons in Bilayer Graphene with Opened Energy Gap

Abstract

In this work we study excitonic absorption in bilayer graphene where an energy gap is opened by a static perpendicular electric field. On the basis of the tight-binding approach and second quantized Hamiltonian the linearized quantum kinetic equations for the density matrix are obtained. It is shown that the exciton binding energy and intensity of the excitonic absorption can be tuned by changing the value of the gap and tight-binding parameters. It is found that the account of circular asymmetry of the energy bands in bilayer graphene leads to a strong increase of exciton binding energy and excitonic absorption.