Giant anharmonicity suppresses superconductivity in AlH$_3$ under pressure

TL;DR

This study calculates anharmonic phonon effects in AlH$_3$ under high pressure, revealing that strong anharmonicity suppresses electron-phonon coupling and likely reduces superconductivity, explaining previous experimental-theoretical discrepancies.

Contribution

It provides the first detailed calculation of anharmonic phonon self energies in AlH$_3$ at high pressure, showing their significant impact on superconductivity predictions.

Findings

Anharmonic phonon self energies are very large.

Anharmonicity suppresses the electron-phonon coupling parameter λ.

This suppression explains the discrepancy between experiments and previous theories.

Abstract

The anharmonic self energy of two zone boundary phonons were computed to lowest order for AlH$_3$ in the $Pm\bar 3n$ structure at 110 GPa. The wavevector and branch index corresponding to these modes are situated in a region of phase space providing most of the electron-phonon coupling. The self energies are found to be very large and the anharmonic contribution to the linewidth of one of the modes studied could be distinguished from the electron-phonon linewidth. It is found that anharmonicity suppresses the electron-phonon coupling parameter $\lambda$, providing a possible explanation for the disagreement between experiment and previous theoretical studies of superconductivity in this system.