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Kohn anomalies in superconductors
Journal article   Open access   Peer reviewed

Kohn anomalies in superconductors

Michael E. Flatté
Physical review. B, Condensed matter, Vol.50(2), pp.1190-1198
07/01/1994
DOI: 10.1103/PhysRevB.50.1190
PMID: 9975790
url
https://arxiv.org/pdf/cond-mat/9306015View
Open Access

Abstract

The detailed behavior of phonon dispersion curves near momenta which span the electronic Fermi sea in a superconductor is presented. An anomaly, similar to the metallic Kohn anomaly, exists in a superconductor's dispersion curves when the frequency of the photon spanning the Fermi sea exceeds twice the superconducting energy gap. This anomaly occurs at approximately the same momentum but is stronger than the normal-state Kohn anomaly. It also survives at finite temperature, unlike the metallic anomaly. Determination of Fermi-surface diameters from the location of these anomalies, therefore, may be more successful in the superconducting phase than in the normal state. However, the superconductor's anomaly fades rapidly with increased phonon frequency and becomes unobservable when the phonon frequency greatly exceeds the gap. This constraint makes these anomalies useful only in high-temperature superconductors such as La1.85Sr0.15CuO4. © 1994 The American Physical Society.

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