Phase Diagram and High-Temperature Superconductivity of Compressed Selenium Hydrides

TL;DR

This study predicts stable high-temperature superconducting phases in compressed selenium hydrides, revealing new phases and superconductivity up to 110 K, expanding the understanding of light-element superconductors.

Contribution

It provides the first comprehensive first-principles analysis of selenium hydrides, identifying stable metallic phases and their superconducting properties under high pressure.

Findings

Stable metallic phases HSe2, HSe, H3Se identified above 120 GPa.

HSe and H3Se exhibit high Tc of 40-110 K.

Selenium hydrides show different phase stability compared to sulfur hydrides.

Abstract

Recent discovery of high-temperature superconductivity (Tc = 190 K) in sulfur hydrides at megabar pressures breaks the traditional belief on the Tc limit of 40 K for conventional superconductors, and open up the doors in searching new high-temperature superconductors in compounds made up of light elements. Selenium is a sister and isoelectronic element of sulfur, with a larger atomic core and a weaker electronegativity. Whether selenium hydrides share similar high-temperature superconductivity remains elusive, but it is a subject of considerable interest. First-principles swarm structure predictions are performed in an effort to seek for energetically stable and metallic selenium hydrides at high pressures. We find the phase diagram of selenium hydrides is rather different from its sulfur analogy, which is indicates by the emergence of new phases and the change of relative stabilities. Three stable and metallic species with stoichiometries of HSe2, HSe and H3Se are identified above ~120 GPa and they all exhibit superconductive behaviors, of which the hydrogen-rich HSe and H3Se phases show high Tc in the range of 40-110 K. Our simulations established the high-temperature superconductive nature of selenium hydrides and provided useful route for experimental verification.