Giant anharmonicity suppresses superconductivity in AlH3 under pressure

Abstract

The anharmonic self-energy of two zone boundary phonons were computed to lowest order for AlH3 in the Pm3̅ n structure at 110 GPa. The wave vector 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 λ, providing a possible explanation for the disagreement between experiment and previous theoretical studies of superconductivity in this system.