Fluctuation-Induced Excess Conductivity and Infrared Spectra in Y Doped BSCCO Superconductors

Abstract

We report here the fluctuation induced excess conductivity and IR spectra in Bi₂Sr₂Ca_1-xY_xCu₂Oy (0.00 < x < 0.50) superconductors. This work is done by using the reported data of Sedky, Physica B 410, 227 (2013), and with the help of Anderson and Zou relation. The logarithmic plots of excess conductivity ∆σ and reduced temperature Є reveal two different exponents corresponding to unique crossover temperature in the slope of each plot. The first exponent is obtained in the normal field region at a temperature of (T_c^mf << T < 2T_c^mf ), while the second exponent is obtained in the mean field region at a temperature of (T ~ T_c^mf). The dimensional exponents are shifted from three dimensional (3D) to two dimensional (2D) for x < 0.30, but it is shifted from 2D to 3D for x = 0.50. Both zero kelvin critical magnetic fields and current density are considerably enhanced by increasing x up to 0.30 followed by a decrease with further increase of x up to 0.50. The vice is versa for the behavior of interlayer coupling, coherence lengths and anisotropy against x. On the other hand, IR spectra show absorption modes in the wave number range of 716-726 cm^-1 according to the value of x. These results are discussed in terms of the correlation between carrier concentration, oxygen deficient and effective Cu valance which are induced by Y through CuO₂ planes of BSCCO superconductors.