Superconductivity in the Chalcogens up to Multimegabar Pressures

Abstract

Highly sensitive magnetic susceptibility techniques were used to measure the superconducting transition temperatures in S up to 231($\pm$5) GPa. S transforms to a superconductor with T$_c$ of 10 K and has a discontinuity in T_c dependence at 160 GPa corresponding to bco to beta-Po phase transition. Above this pressure T_c in S has a maximum reaching about 17.3(+/-0.5) K at 200 GPa and then slowly decreases with pressure to 15 K at 230 GPa. This trend in the pressure dependence parallels the behavior of the heavier members Se and Te. Superconductivity in Se was also observed from 15 to 25 GPa with T_c changing from 4 to 6 K and above 150 GPa with T_c of 8 K. Similiarities in the T_c dependences for S, Se, and Te, and the implications for oxygen are discussed.