Possible Mechanism for Superconductivity in Sulfur - Common Theme for Unconventional Superconductors?

Abstract

Sulfur has recently been found to be a superconductor at high pressure. At ~93 GPa Tc is 10.1 K, and the sulfur is in a base-centered orthorhombic (b.c.o) structure. At ~160 GPa Tc is 17 K and sulfur is in a rhobohedral (b-Po) structure. The mechanism for superconductivity in sulfur is not known; in particular, a band-structure calculation does not find superconductivity in sulfur until 500 GPa. Following work by Anderson, in a 2D strongly interacting non-fermi liquid system with some degree of disorder at T=0, the only known conducting state is a superconductor. Following this idea it has been suggested that both the HTc cuprates and the 2D electron gas systems are superconductors with planar conducting planes. Similarly, here we suggest that the mechanism for conductivity in sulfur are 2D conducting planes which emerge as the planare rings in sulfur at lower pressure pucker at higher pressures (b.c.o. and b-Po). As well, we note some other consequences for study of HTc materials of Anderson's work.