Pressure Induced Spectral Redistribution due to Te₂ Dimer Breaking in AuTe₂

We report the electronic structure of a natural mineral calaverite AuTe₂ under high pressure by means of the infrared spectroscopy. The optical conductivity at ambient pressure shows a Drude response and a hump structure around 0.2 eV. These characteristic results are more prominent in going from high temperature to low temperature. The Drude response increases with pressure, which corresponds to the reduction of the electrical resistivity. Meanwhile, the hump structure is suppressed and merged into the Drude response with increasing pressure. Further applying pressure up to 3 GPa, the hump structure almost disappears. We have fitted the optical conductivity by using the Drude–Lorentz model and obtained the plasma frequency ω_p and the scattering rate γ. The squared plasma frequency !²_p increases and the scattering rate γ decreases with pressure. Our results suggest that the suppression of the electrical resistivity under pressure is mainly due to the increase of the carrier density n and the reduction of the scattering rate γ. By comparing the optical conductivity with the band structure calculation and the photoemission spectroscopy, we discuss the low-energy excitation corresponding to the hump structure and the variation of the Drude component in the optical conductivity.