Suppression of the superconducting phase in new structures of elemental sulfur at terapascal pressures

Abstract

We perform a computational structure search and study the phase diagram of elemental sulfur up to 100 TPa from first-principles using ab initio random structure searching (airss), discovering six new phases with the transition sequence bcc→I41/acd→cI16→α-U→hcp→A15→bcc. The electronic properties and charge density distributions of the new phases are extensively studied. Remarkably, upon transition to the I41/acd phase at 1.24 TPa, the superconducting critical temperature of sulfur abruptly drops from 12 K to just 0.4 K, and above 5 TPa, we find the critical temperature to be zero up to at least 100 TPa. We show that this sudden suppression of superconductivity is coincident with the formation of a sequence of electride phases, which feature significantly reduced electron-phonon coupling and substantial charge localization. Despite ceasing to be a superconductor, sulfur remains metallic up to at least 100 TPa.

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