Anharmonic phonon damping enhances the Tc of BCS-type superconductors

Chandan Setty; Matteo Baggioli; Alessio Zaccone

doi:10.1103/PhysRevB.102.174506

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Anharmonic phonon damping enhances the Tc of BCS-type superconductors

Chandan Setty, Matteo Baggioli, Alessio Zaccone

DOI 10.1103/PhysRevB.102.174506 · Physical Review B

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Abstract

A theory of superconductivity is presented where the effect of anharmonicity, as entailed in the acoustic, or optical, phonon damping, is explicitly considered in the pairing mechanism. The gap equation is solved including diffusive Akhiezer damping for longitudinal acoustic phonons or Klemens damping for optical phonons, with a damping coefficient which, in either case, can be directly related to the Grüneisen parameter and hence to the anharmonic coefficients in the interatomic potential. The results show that the increase of anharmonicity has a strikingly nonmonotonic effect on the critical temperature Tc. The optimal damping coefficient yielding maximum Tc is set by the velocity of the bosonic mediator. This theory may open up unprecedented opportunities for material design where Tc may be tuned via the anharmonicity of the interatomic potential, and presents implications for the superconductivity in the recently discovered hydrides, where anharmonicity is very strong and for which the anharmonic damping is especially relevant.