Refractive index of GaTe under high pressure
In this paper we describe two experiments, in the near- and mid-infrared, designed to investigate the evolution under pressure of the GaTe refractive index for polarization parallel and perpendicular to the crystallographic c-axis (in the layer plane). The refractive index dispersion for both light polarizations has been determined up to 5.5 GPa. It is found that the refractive index increases faster in the direction perpendicular to the c-axis than along the c-axis. To find out the origin of such a difference we used a Phillips-Van Vechten model and arrived at the conclusion that it is due to the different pressure behaviour of the Penn gap for each polarization.