Strong light-matter interaction in systems described by a modified Dirac equation

The bulk states of some materials, such as topological insulators, are described by a modified Dirac equation. Such systems may have trivial and non-trivial phases. In this paper, we show that in the non-trivial phase a strong light-matter interaction exists in a two-dimensional system, which leads to an optical conductivity at least one order of magnitude larger than that of graphene.