\documentclass[12pt]{article}
\usepackage{amsmath,amssymb,amsfonts}
\begin{document}
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 an ultrathin film of 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 non-trivial phase of the system and the optical Hall conductivity changes sign at transition from trivial to non-trivial phases which has significant consequences on a circular polarization and optical absorption of the system.
\end{document}