Possible enhancement of the superconducting Tc due to sharp Kohn-like soft phonon anomalies
- 24 February 2023
- journal article
- research article
- Published by IOP Publishing in Journal of Physics: Condensed Matter
- Vol. 35 (16), 164003
- https://doi.org/10.1088/1361-648x/acbd0a
Abstract
Phonon softening is a ubiquitous phenomenon in condensed matter systems which is often 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. Model calculations show that the phonon softening in the form of a sharp 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 lambda. 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 T-c. In summary, our results suggest the possibility of reaching high-temperature superconductivity by exploiting soft phonon anomalies restricted in momentum space.Funding Information
- US Army Research Office (W911NF-22-2-0256)
- European Union through Horizon Europe ERC Grant (101043968)
- Shanghai Municipal Science and Technology Major Project (2019SHZDZX01)
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