High-temperature study of superconducting hydrogen and deuterium sulfide

TL;DR

This study uses Eliashberg theory to analyze thermodynamic properties of hydrogen sulfide and its isotope, deuterium sulfide, under high pressure, revealing strong-coupling effects and pressure-independent isotope effects on superconductivity.

Contribution

It provides a detailed comparison of thermodynamic properties of H₃S and D₃S using Eliashberg theory, highlighting the significance of strong-coupling and retardation effects.

Findings

Reproduces critical temperatures of 203 K for H₃S and 147 K for D₃S.

Shows strong-coupling effects cause deviations from BCS predictions.

Discusses isotope effect independence from pressure.

Abstract

Hydrogen-rich compounds are extensively explored as candidates for a high-temperature superconductors. Currently, the measured critical temperature of $203$ K in hydrogen sulfide (H$_3$S) is among the highest over all-known superconductors. In present paper, using the strong-coupling Eliashberg theory of superconductivity, we compared in detail the thermodynamic properties of two samples containing different hydrogen isotopes H$_3$S and D$_3$S at $150$ GPa. Our research indicates that it is possible to reproduce the measured values of critical temperature $203$ K and $147$ K for H$_3$S and D$_3$S by using a Coulomb pseudopotential of $0.123$ and $0.131$, respectively. However, we also discuss a scenario in which the isotope effect is independent of pressure and the Coulomb pseudopotential for D$_3$S is smaller than for H$_3$S. For both scenarios, the energy gap, specific heat, thermodynamic critical field and related dimensionless ratios are calculated and compared with other conventional superconductors. We shown that the existence of the strong-coupling and retardation effects in the systems analysed result in significant differences between values obtained within the framework of the Eliashberg formalism and the prediction of the Bardeen-Cooper-Schrieffer theory.