Charge transfer mechanism and Tc(x) dependence in Y0.8(Ca)0.2Ba2Cu3O6+x
Abstract
We propose a model for charge transfer mechanism in Y0.8(Ca)0.2Ba2Cu3O6+x to count hole doping of CuO2 planes and x dependence of critical transition temperature Tc. It is assumed the total number of doped holes in the planes is sum of holes that are introduced through two separate channels: substitution of Y3+ by Ca2+ and from CuO chains that are longer than a minimal (critical) length lmin needed for charge transfer to take place. The Tc(x) dependence is obtained by combining calculated x dependence of doping, p(x), and universal Tc versus p relation. Although calculated Tc(x) dependences for lmin=3 and lmin=4 both remarkably correlate to the experimental Tc(x), we argue that the value lmin=4 gives a reasonable overall agreement.
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