Understanding the Role of Anharmonicity in Superconductivity

Since its formulation and discovery there has been considerable interest in pushing the bounds of superconductivity in condensed matter systems. The main focus in this endeavor has been to increase the pairing strength without affecting long range coherence of the system. Here we report on Raman measurements performed on a series of topological semimetals where the electronic and phonon structures can be tuned without any change in disorder. Despite BCS predictions, some of the compounds in the series exhibit a strong suppression of the superconducting state. Careful analysis reveals the lifetimes of the phonons in the superconducting compounds shows strong phonon-electron coupling while the non-superconducting compounds exhibit lifetimes consistent with strong anharmonic decay allowing us to determine the microscopic mechanism behind the suppression of superconductivity.