Direct Optical Observation of the Semiconductor-to-Metal Transition in SmS under Pressure

Abstract

A discontinuous change in the reflectivity due to the first-order semiconductor-to-metal transition has been observed in SmS at a pressure of about 6 kbar. The metallic state is characterized by a golden yellow luster which arises because of interband transitions superimposed on the Drude reflectivity. These results and the pressure dependence of the optical-absorption edge in semiconducting SmSe and SmTe are in excellent agreement with earlier resistivity measurements.