Return to index
Abstract:
We calculate the absorptive part of the frequency-dependent conductivity for a large class of
anisotropic superconductors. The effect of nonmagnetic impurity scattering is included at the
level of a self-consistent t-matrix approximation. It is found that low-frequency absorption
(0 < Ω < 2Δ)
takes place for any superconducting state with nodes of the
energy gap on the Fermi surface. We demonstrate that the limiting low-frequency dependence of
σ(Ω) on impurity concentrations can help to determine the structure of the order
parameter in candidate systems such as heavy-electron compounds
or high-Tc superconductors.
We also discuss how strong scattering, similar to that observed in ordinary
superconductors doped with Kondo impurities, may lead to absorption with a threshold of
Ω ≈ Δ rather than 2Δ as in quasiisotropic systems.
Finally, we consider the contribution of order-parameter
collective modes to the electromagnetic absorption, and show that this absorption may be
substantial and depends sensitively on the impurity scattering rate.
Paper: [PDF]
Return to index