Effect of hexagonal warping of the Fermi surface on the thermoelectric properties of a topological insulator irradiated with linearly polarized radiation

Abstract

We investigate the effect of the hexagonal warped anisotropic Fermi surface on the anomalous thermoelectric properties of the topological insulator surface illuminated with linearly polarized off-resonant electromagnetic radiation. Upon irradiation of the TI surface, the linearly polarized (LP) off-resonant radiation couples with the Dirac surface states. By explicitly finding the off-resonant quasistatic Hamiltonian we show that this coupling occurs only in the presence of the hexagonal warping of the Fermi surface of the topological insulator. We calculate the spin texture of the surface states, Berry curvature, Berry phase, orbital magnetic moment, and magnetization associated with the band structure, which we find strongly depends on the angle of polarization and the amplitude of radiation. For the anomalous thermoelectric effects generated by the Berry curvature, it is found that due to the hexagonal warping induced Fermi surface deformation and the radiation parameter dependent spin texture of the surface states, the transverse Hall, Ettingshausen, Nernst, and thermal conductivities show significant variation with the change in polarization angle, chemical potential, temperature, and the amplitude of radiation. As a consequence, the thermoelectric coefficient of performance ($ZT$) of the topological insulator is found to be increased in the presence of LP off-resonant irradiation compared to the absence of radiation.