Intrinsic optical conductivity of modified Dirac fermion systems

We analytically calculate the intrinsic longitudinal and transverse optical conductivities of electronic systems which govern by a modified Dirac fermion model Hamiltonian for materials beyond graphene such as monolayer MoS2 and ultrathin film of the topological insulator. We analyze the effect of a topological term in the Hamiltonian on the optical conductivity and transmittance. We show that the optical response enhances in the nontrivial phase of the ultrathin film of the topological insulator and the optical Hall conductivity changes sign at transition from trivial to nontrivial phases which has significant consequences on the circular dichroism property and optical absorption of the system.