Vital influence of hydrogen σ antibonding states on high−Tc superconductivity in SH3 under ultrahigh …

Achieving high-${T}_{c}$ superconductivity in hydrogen-rich materials under ultrahigh pressure relies crucially on the metallization of strong $\ensuremath{\sigma}$ bonding or antibonding electrons. It is essential to discern the bonding characters of superconducting electrons in order to unveil the underlying high-${T}_{c}$ pairing mechanism in these materials. In this study, we investigate the electronic and phonon properties of hydrogen sulfide (${\mathrm{SH}}_{3}$) under ultrahigh pressure to elucidate the origin of its high-${T}_{c}$ superconductivity. Contrary to the prevailing belief attributing the high-${T}_{c}$ superconductivity to the contribution of the metallized S-H $\ensuremath{\sigma}$ bonds, our analysis, based on the solution of the anisotropic Migdal-Eliashberg equation and the crystal orbital Hamilton population calculation, reveals that the H-H $\ensuremath{\sigma}$ antibonding states play a decisive role in the large electron-phonon coupling that leads to the superconducting pairing in ${\mathrm{SH}}_{3}$. Furthermore, by partially restricting the vibration of S atoms, we show that the S-H bonds only provide subsidiary contributions to the pairing interaction. These findings not only shed light on the importance of the H-H $\ensuremath{\sigma}$-antibonds in driving high-${T}_{c}$ superconductivity in ${\mathrm{SH}}_{3}$, but crucially they pave the way for a profound understanding of the intricate connection between metallic H-H $\ensuremath{\sigma}$ antibonding states and high-${T}_{c}$ superconductivity in a diverse array of hydrogen-rich materials subjected to high-pressure environments.