The quantum nature of the superconducting hydrogen sulfide at finite temperatures

TL;DR

This study uses ab initio path-integral molecular dynamics to show that nuclear quantum effects significantly influence the structure and isotope-dependent superconducting transition temperature of hydrogen sulfide at high pressures, highlighting its quantum nature.

Contribution

It demonstrates the importance of nuclear quantum effects in understanding the isotope dependence of superconductivity in hydrogen sulfide using advanced simulation methods.

Findings

Nuclear quantum effects cause different structural behaviors in H3S and D3S at finite temperatures.

The symmetric high Tc structure exists in H3S but not in D3S within certain pressure ranges.

Discrepancies with experimental Tc values can be reduced with hybrid functional electronic structure calculations.

Abstract

H$_3$S is believed to the most possible high-temperature superconducting ($T_{\text{c}}$) phase of hydrogen sulfide at $\sim$200 GPa. It's isotope substitution of hydrogen (H) by deuterium (D), however, shows an anomalous $T_{\text{c}}$ decrease of $\sim$100 K at 140 to 160 GPa, much larger than the Bardeen-Cooper-Schrieffer theory prediction. Using ab initio path-integral molecular dynamics (PIMD), we show that the nuclear quantum effects (NQEs) influence the structures of H$_3$S and D$_3$S differently at finite temperatures and the interval when H$_3$S possesses the symmetric high $T_{\text{c}}$ structure while D$_3$S does not is in agreement with, though their absolute values are lower than experiments. This is consistent with an earlier theoretical study using the stochastic self-consistent harmonic approximation method in descriptions of the nuclei at 0 K.The remaining discrepancy can be substantially improved when the electronic structures are calculated using a hybrid function. Our study presents a simple picture to interpret the isotope dependent of $T_{\text{c}}$ and emphasizes the quantum nature in the high-pressure hydrogen sulfide system.