Optical properties of px + ipy superconductors with strong impurities
P. A. Ioselevich+*, P. M. Ostrovsky*×
+National Research University Higher School of Economics, 101000 Moscow, Russia
*L. D. Landau Institute for Theoretical Physics, 119334 Moscow, Russia
×Max-Planck-Institute for Solid State Research, 70569 Stuttgart, Germany
Abstract
We study effects of strong impurities on optical properties of a chiral px + ipy superconductor with broken time-reversal symmetry. Potential impurities
create subgap states in the superconductor's spectrum similar to
Yu-Shiba-Rusinov states on magnetic impurities in a conventional
superconductor. We
calculate the average density of states and find both the profile of the subgap
impurity band due to localized states and modifications to the continuous
spectrum above the gap. We also consider the anomalous Hall response of the
superconductor at arbitrary frequencies and temperatures arising due to skew
scattering on impurities. Hall conductivity is responsible for the polar Kerr
effect and can be directly measured in an optical experiment. Frequency
dependence of the Hall conductivity exhibits a rich structure corresponding to
various possible transitions of quasiparticles between superconducting
condensate, localized impurity states, and continuous spectrum above the gap.