Microwave conductivity ofd-wave superconductors with extended impurities

Abstract

We investigate the influence of extended scatterers on the finite temperature and finite frequency microwave conductivity of d-wave superconductors. For this purpose we generalize a previous treatment by Durst and Lee [Ref. 22], which is based on a nodal approximation of the quasiparticle excitations and scattering processes, and apply it to the analysis of experimental spectra of YBCO-123 and BSCCO-2212. For YBCO, we find that accounting for a slight spatial extension of the strong scattering in-plane defects improves the fit of the low temperature microwave conductivity to experiment. With respect to BSCCO we conclude that it is necessary to include a large concentration of weak-to-intermediate strength extended scatterers, which we attribute to the out-of plane disorder introduced by doping. These findings for BSCCO are consistent with similar analyses of the normal state ARPES spectra and of STM spectra in the superconducting state, where an enhanced forward scattering has been inferred as well.

Electrical transport measurements in the superconducting state ofBi2Sr2CaCu2O8

“…5, with a large residual conductivity σ 1 (T → 0) at low frequencies that becomes small at the higher frequencies. The ability of Nunner et al to fit our Bi 2 Sr 2 CaCu 2 O 8+x microwave data within the SCTMA framework using a combination of dilute strong scatterers and a high density of weak-scattering extended defects 14 suggests that a similar calculation might account for the terahertz data.…”

Oxygen chain disorder as a weak-limit scatterer in YBa2Cu3O6.50

“…The model presented in Ref. 23 led to a plausible understanding of the temperature dependence of the quasiparticle conductivity, using defect densities typical of this material. The data sets presented here are ideal for this treatment since the off-plane disorder dominates the quasiparticle transport, but unlike BSCCO this disorder is considerably smaller and can be easily manipulated in a single sample.…”

Anisotropic microwave conductivity of cuprate superconductors in the presence of CuO chain-induced impurities

“…12 , and have been determined by the self-consistent calculation 13,14 . In the presence of impurities, the unperturbed electron Green's function (3) is dressed via the impurity scattering 18,19,20 ,…”

“…In this CuO 2 plane isotropic case, a general scattering potential V kk ′ need only be evaluated in three possible cases 18,19 : the intranode impurity scatter-…”

“…In the above discussions of the low temperature and low energy case, the inelastic quasiparticle-quasiparticle scattering process has been dropped, since it is suppressed at low temperatures and low energies due to the large SC gap parameter in the quasiparticle excitation spectrum. For a better understanding of the anisotropy in the microwave conductivity spectrum, we now turn to discuss the temperature dependence of the quasiparticle transport of the ortho-II YBa 2 Cu 3 O 6.50 , where T may approach to T c from low temperature side, and therefore the inelastic quasiparticle-quasiparticle scattering process should be considered 19 . The contribution from this inelastic quasiparticle-quasiparticle scattering process is increased rapidly when T approaches to T c from low temperature side, since there is a small SC gap parameter near T c .…”