Intrinsic optical conductivity of a ${{\rm{C}}}_{2v}$ symmetric topological insulator

In this work we analytically investigate the longitudinal optical conductivity of the C-2v symmetric topological insulator. The conductivity expressions at T = 0 are derived using the Kubo formula and expressed as a function of the ratio of the Dresselhaus and Rashba parameters that characterize the low-energy Hamiltonian. We find that the longitudinal inter-band conductivity vanishes when Dresselhaus and Rashba parameters are equal in strength, also called the persistent spin helix state. The calculations are extended to obtain the frequency-dependent real and imaginary components of the optical conductivity for the topological Kondo insulator SmB6 which exhibits C-2v symmetric and anisotropic Dirac cones hosting topological states at (X) over bar point on the surface Brillouin zone.