Causes of high-temperature superconductivity in the hydrogen sulfide electron-phonon system

TL;DR

This paper investigates the structural, electronic, and phononic properties of hydrogen sulfide under high pressure, revealing a quasi-two-dimensional electron system and specific phonon features linked to high-temperature superconductivity.

Contribution

It provides detailed calculations of spectra and structural changes in hydrogen sulfide at high pressures, elucidating mechanisms behind its superconductivity.

Findings

Formation of hydrogen atom planes at ~175 GPa

Quasi-two-dimensional electron properties observed

Identification of high-energy phonon peaks

Abstract

The electron and phonon spectra, as well as the density of electron and phonon states of the stable orthorhombic structure of hydrogen sulfide (SH2) at pressures 100-180 GPa have been calculated. It is found that the set of parallel planes of hydrogen atoms is formed at pressure ~175 GPa as a result of structural changes in the unit cell of the crystal under pressure. There should be complete concentration of hydrogen atoms in these planes. As a result the electron properties of the system acquire a quasi-two-dimensional character. The features of in phase and antiphase oscillations of hydrogen atoms in these planes leading to two narrow high-energy peaks in the phonon density of states are investigated.