Effect of impurity scattering on a (d+s)-wave superconductor

Abstract

Recent measurements of the surface impedance in YBa2Cu307~single crystals show large in-plane anisotropy which implies that orthorhombicity due to the Cu-0 chains is not small. In addition, the controversy between the d-wave and the s-wave order parameter persists. In the framework of the orthorhombic symmetry, an order parameter with (d+ s)-wave symmetry is considered in an attempt to understand current experimental results. We provide a detailed study of the characteristics of such an order parameter in the low-temperature behavior of the penetration depth, the density of states, and the T, suppression in the presence of nonmagnetic impurity scattering. The results are discussed in comparison with the d-wave and the anisotropic s-wave cases.

Coherent Control of Absorption and Polarization Decay in a GaAs Quantum Well: Time and Spectral Domain Studies

“…This is possible only by decreasing the coherent exciton polarization that was prepared by the first pulse. After the transmission and distortion of the second pulse, the upconverted intensity shows a polarization decay with modulation due to the HH-LH quantum beats [14,15], which is a measure of the remaining exciton polarization. Because of the vanishingly small solid angle probed by our experiment and subpicosecond time scale, this polarization decay is by far the dominant contribution in the directions parallel and antiparallel to the excitation, completely overshadowing any contribution from luminescence.…”

Ginzburg-Landau equation and the upper critical field in anisotropic (d+s)-wave superconductivity

“…9 except for crucial differences which are the following: we incorporate here a repulsive Coulomb interaction in the s channel and our interaction is nonseparable, in contrast with the one in Ref. 9. The Coulomb term, in particular, opens up the possibility that the admixture with the s component can be a normal phase density-of-states effect.…”

“…8 The simplest model to account for the normal phase anisotropy is provided in Ref. 9 assuming an elliptical Fermi surface. Then the density of states and the Fermi velocities in the x and y directions are, respectively, given by 8…”

Ultrasonic attenuation in an orthorhombic anisotropic superconductor

“…Additional effects of band anisotropy, i.e., orthorhombicity, include important changes in residual density of states in the presence of elastic impurity scattering. 5,6 A finite density of states at zero energy can drastically affect the observed lowtemperature properties that depend mainly on the behavior around the gap nodes. To understand these effects better, it is important to have more experiments that reveal details of gap and band anisotropies.…”