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TT: Fachverband Tiefe Temperaturen

TT 63: Superconductivity: Theory

TT 63.1: Talk

Friday, March 31, 2023, 09:30–09:45, HSZ 103

Sharp Kohn-like phonon anomalies due to charge order can strongly enhance the superconducting Tc — •Alessio Zaccone — Department of Physics, University of Milan, 20133 Milano, Italy

Phonon softening is a ubiquitous phenomenon in condensed matter systems which is usually associated with charge density wave (CDW) instabilities and anharmonicity. The interplay between phonon softening, CDW and superconductivity is a topic of intense debate. In this work, the effects of anomalous soft phonon instabilities on superconductivity are studied based on a recently developed theoretical framework that accounts for phonon damping and softening within the Migdal-Eliashberg theory [1]. Model calculations [2] show that the phonon softening in the form of a dip in the phonon dispersion relation, either acoustic or optical (including the case of Kohn-type anomalies typically associated with CDW), can cause a manifold increase of the electron-phonon coupling constant λ. This, under certain conditions, which are consistent with the concept of optimal frequency introduced by Bergmann and Rainer, can produce a large increase of the superconducting transition temperature Tc. These results suggest the possibility of reaching high-temperature superconductivity by exploiting soft phonon anomalies restricted in momentum space.
[1] M. Baggioli, C. Setty, A. Zaccone, Phys. Rev. B 101, 214502 (2020)
[2] arXiv:2211.12015v2

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