Pressure-induced exciton formation and superconductivity in platinum-based mineral Sperrylite

TL;DR

This study investigates Sperrylite (PtAs2) under high pressure, revealing pressure-induced excitonic states and a transition to superconductivity at pressures above 92 GPa, with no structural phase change observed.

Contribution

It provides the first detailed high-pressure analysis of Sperrylite, linking electronic band structure evolution to excitonic states and superconductivity without structural phase transitions.

Findings

Superconductivity appears above 92 GPa at ~3 K.

Electronic band structure shows a Lifshitz transition under pressure.

Pressure induces excitonic states linked to superconductivity.

Abstract

We report a comprehensive study of Sperrylite (PtAs2), the main platinum source in natural minerals, as a function of applied pressures up to 150 GPa. While no structural phase transition was detected from pressure-dependent X-ray measurements, the unit cell volume shrinks monotonically with pressure following the third-order Birch-Murnaghan equation of state. The mildly semiconducting behavior found in pure synthesized crystals at ambient pressures becomes more insulating upon increasing applied pressure before metalizing at higher pressures, giving way to the appearance of an abrupt decrease in resistance near 3 K at pressures above 92 GPa consistent with the onset of a superconducing phase. The pressure evolution of the calculated electronic band structure reveals the same physical trend as our transport measurements, with a non-monotonic evolution explained by a hole band that is pushed below the Fermi energy and an electron band that approaches it as a function of pressure, both reaching a touching point suggestive of an excitonic state. A topological Lifshitz transition of the electronic structure and an increase in the density of states may naturally explain the onset of superconductivity in this material