TY - JOUR
T1 - A dynamic Jahn-Teller theory for high-Tc superconductivity
AU - Weger, M.
AU - Englman, R.
PY - 1990/9/1
Y1 - 1990/9/1
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=44949290558&partnerID=8YFLogxK
U2 - 10.1016/0378-4371(90)90384-5
DO - 10.1016/0378-4371(90)90384-5
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AN - SCOPUS:44949290558
SN - 0378-4371
VL - 168
SP - 324
EP - 337
JO - Physica A: Statistical Mechanics and its Applications
JF - Physica A: Statistical Mechanics and its Applications
IS - 1
ER -