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 β-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.