Superconductivity in the chalcogens up to multimegabar pressures

Highly sensitive magnetic-susceptibility techniques were used to measure the superconducting transition temperatures in S up to 231(+/-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 the 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 the highest pressures measured. This trend in the pressure dependence parallels the behavior of the heavier chalcogens Se and Te. Superconductivity in Se was 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. Similarities in the T-c dependences for S, Se, and Te, and implications for oxygen are discussed.