A dynamic Jahn-Teller theory for high-Tc superconductivity

M. Weger*, R. Englman

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

12 Scopus citations

Abstract

The Jahn-Teller effect gives rise to a negative McMillan coupling constant λ. This negative λ gives rise to oscillatory solutions of the BCS gap function Δ(E). The period of oscillations is given (approximately) by 4 3ω, where ω is the phonon or exciton frequency. These oscillations require an Einstein spectrum, or at least small dispersion. The oscillatory solutions are insensitive to the (non-resonant) Coulomb repulsion μ. They are obtained from the Dyson equation, which serves as a starting point of the Eliashberg theory, but not from the Eliashberg equation per se. We suggest that the singular nature of these solutions requires a minor modification of Eliashberg's derivation. These solutions are particularly favorable for excitonic superconductivity, for which the range of interaction η= 3 2πvF/ω is one, or a few, lattice constants, and the Cooper pairs have some "boson" character. We suggest that these solutions arise because the conditions required for the validity of Migdal's theorem do not hold.

Original languageEnglish
Pages (from-to)324-337
Number of pages14
JournalPhysica A: Statistical Mechanics and its Applications
Volume168
Issue number1
DOIs
StatePublished - 1 Sep 1990

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