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 ∼ in the boson spectrum: bosons at ω< are pair breaking. We give an approximate expression for the pair-breaking effect of low-lying bosons. We also study the dependence of upon g in an Einstein model in which the boson spectral weight is concentrated at a frequency . We show that for fixed electron-boson coupling, / decreases rapidly as g decreases from 1, and for g≠1 / saturates at a low value as the coupling tends to infinity. Applications to heavy-fermion superconductors and to the new high- materials are discussed.
- Received 9 November 1987
DOI:https://doi.org/10.1103/PhysRevB.37.4975
©1988 American Physical Society