Superconductivity of TaS2-xSexlayer compounds at high pressure

Abstract

The superconducting transition temperatures for layer compounds in the system TaS_2-xSe_x have been measured as a function of hydrostatic pressure up to 25 kbar. When the coordination of the metal atoms is purely trigonal prismatic, T_c is strongly enhanced by pressure, whereas for mixed octahedral-trigonal prismatic coordination the increase of T_c is very much smaller. Increasing the interlayer spacing by intercalation reduces the influence of pressure upon T_c such that for expansions >or=6 AA T_c is essentially independent of pressure. It is suggested that an increase in the overlap of the d_z2 wavefunctions in the interlayer region is responsible for the increase of T_c.