Optical conductivity and tunable linear dichroism of surface states in strained three-dimensional topological insulators

We theoretically investigate the influence of anisotropic shear strain on the optical conductivity and linear dichroism of surface states in three-dimensional topological insulators. By employing an effective two-band Hamiltonian that incorporates strain-induced modifications, we demonstrate that the applied strain significantly deforms the Dirac cone, leading to pronounced anisotropy in the Fermi velocities and optical conductivities. The resulting linear dichroism is shown to be highly tunable with the magnitude and direction of strain, notably enabling reversible control through dichroism sign inversion. Polar plots of angle-resolved optical conductivity clearly reveal the selective enhancement or suppression of polarized light absorption along specific crystallographic orientations for various strain configurations. These findings suggest the potential for mechanical modulation of polarization-sensitive absorption in three-dimensional topological insulators.