Far-Infrared Spectroscopy of Electronic States of CuIr2Se4 at High Pressure

Abstract

The spinel compound CuIr 2 Se 4 at atmospheric pressure is a metal of wide temperature range, but undergoes a stabilization of the insulating phase from the metal phase at high pressures above 3 GPa. To study the change in electronic state at pressure, we performed a spectromicroscopic measurement in the far-infrared to visible region on polycrystalline CuIr 2 Se 4 at high pressures up to 8 GPa at room temperature. The peak structure at around 0.2 eV in the optical conductivity spectra at atmospheric pressure, whose origin was assigned to the hybridized band, was found to lose its intensity at pressure accompanied by the rapid suppression of the Drude component. This change in the optical spectra at pressure indicates that the pseudo-gap state formed in the vicinity of the Fermi level is very sensitive to pressure. We discuss this behaviour in relation to the instability of the metallic state due to the increase in the degree of hybridization with pressure.