Doping and energy dependent microwave conductivity of kinetic energy driven superconductors with extended impurities

Abstract

Within the framework of the kinetic energy driven superconducting mechanism, the effect of the extended impurity scatterers on the quasiparticle transport of cuprate superconductors in the superconducting state is studied based on the nodal approximation of the quasiparticle excitations and scattering processes. It is shown that there is a cusplike shape of the energy dependent microwave conductivity spectrum. At low temperatures, the microwave conductivity increases linearly with increasing temperatures, and reaches a maximum at intermediate temperature, then decreases with increasing temperatures at high temperatures. In contrast with the dome shape of the doping dependent superconducting gap parameter, the minimum microwave conductivity occurs around the optimal doping, and then increases in both underdoped and overdoped regimes.

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

“…This broadening is only attributed to increased quasiparticle scattering arising from the CuO chain induced impurities. In comparison with our previous results for the non-ortho-II phase of cuprate superconductors 12 , the present results of the anisotropy therefore confirm that the CuO chain induced impurity is the dominant source of the anisotropy in the microwave conductivity spectrum of the ortho-II YBa 2 Cu 3 O 6.50 9 . 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.…”

“…It is clearly that the anisotropy of the energy evolution of the low temperature microwave conductivity of the ortho-II YBa 2 Cu 3 O 6.50 is qualitatively reproduced 8,9 , where quasiparticle spectral weights differ by a factor of two between theâ-axis andb-axis directions. Moreover, although the cusplike lineshapes are observed along bothâ-axis andb-axis directions as in the previous case in the non-ortho-II phase of cuprate superconductors 12 , the width of theâ-axis spectrum is significantly broadened. This broadening is only attributed to increased quasiparticle scattering arising from the CuO chain induced impurities.…”

“…3 (inset). Obviously, the overall temperature dependence is similar to that of the temperature dependence of the microwave conductivity in the non-ortho-II phase of cuprate superconductors 12 , where bothâ-axis andb-axis temperature dependent microwave conductivities σ a (ω, T ) and σ b (ω, T ) increases rapidly with increasing temperatures to a broad peak, and then falls roughly linearly. In particular, this broad peak shifts to higher temperatures as the energy increased.…”

“…Now we follow our previous discussions 12 , and obtain explicitly theâ-axis andb-axis microwave conductivities of the ortho-II YBa 2 Cu 3 O 6+y as,…”

“…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 ,…”