Inelastic scattering and pair breaking in anisotropic and isotropic superconductors

A. J. Millis, Subir Sachdev, and C. M. Varma
Phys. Rev. B 37, 4975 – Published 1 April 1988
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Abstract

The pair-breaking effect of inelastic scattering of electrons off boson fluctuations is examined for anisotropic and isotropic superconductors. We show that the ratio g of the couplings of the boson fluctuations to the pairing and normal electron self-energies is an important parameter. Phonon-mediated s-wave superconductivity corresponds to a value of g=1, and spin-fluctuation-mediated d-wave superconductivity to g<1. For g<1, there is a critical frequency ωcTce1/g in the boson spectrum: bosons at ω<ωc are pair breaking. We give an approximate expression for the pair-breaking effect of low-lying bosons. We also study the dependence of Tc upon g in an Einstein model in which the boson spectral weight is concentrated at a frequency ωE. We show that for fixed electron-boson coupling, Tc/ωE decreases rapidly as g decreases from 1, and for g≠1 Tc/ωE saturates at a low value as the coupling tends to infinity. Applications to heavy-fermion superconductors and to the new high-Tc materials are discussed.

  • Received 9 November 1987

DOI:https://doi.org/10.1103/PhysRevB.37.4975

©1988 American Physical Society

Authors & Affiliations

A. J. Millis

  • AT&T Bell Laboratories, Murray Hill, New Jersey 07974

Subir Sachdev

  • AT&T Bell Laboratories, Murray Hill, New Jersey 07974
  • Institute for Theoretical Physics, University of California, Santa Barbara, California 93106

C. M. Varma

  • AT&T Bell Laboratories, Murray Hill, New Jersey 07974

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Issue

Vol. 37, Iss. 10 — 1 April 1988

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