Superconductivity, cuprate doping dependence

The ratio Ap/kTc is nearly constant in the optimal doping region and it increases rapidly with c diminishing from c0. It is possible to speculate on various further properties of cuprates on the basis of the present model. If one asks about the temperature dependence of the normal state gaps, one must incorporate the complicated calculation of Qq T) [8] and account for the fluctuations of the superconductivity order partameter. 

Studies on other high-temperature superconductors Positron annihilation measurements across Tc, coupled with the calculations of PDD have been carried out in a variety of hole-doped superconductors that include YBa2Cu40g [48], Bi-Sr-Ca-Cu-0 [49], and Tl-Ba-Ca-Cu-0 [50, 51] systems. We will not labor with the details here, except to state that a variety of temperature dependencies are seen and these can be rationalized when the results are analysed in terms of positron density distribution and the electron-positron overlap function [39]. These calculations show that the positron s sensitivity to the superconducting transition arises primarily from the ability to probe the Cu-O network in the Cu-0 layer. The different temperature dependencies of lifetime, i.e., both the increase and decrease, can be understood in terms of a model of local electron transfer from the planar oxygen atom to the apical oxygen atom, after taking into account the correct positron density distribution within the unit cell of the cuprate superconductor. 

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