Correlation gap mechanism for Tcdegradation in high-temperature superconductors

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Abstract
It is shown that Altshuler-Aronov-type interaction anomalies affecting the pair propagator yield a degradation of Tc with increasing disorder. For some materials this mechanism allows for a quantitative explanation of the observed degradation effect. Thereby important features are an enhancement of the interaction anomalies due to the attractive BCS interaction as well as a renormalisation of the Coulomb pseudopotential, which becomes dependent on the disorder. The resulting simple formula for Tc is compared with some experiments using realistic parameters. In particular, the resistivity scale needed as an input is extracted from the resistivity saturation phenomena occurring in the normal state. The theory explains the observed correlation between the value of Tc in clean samples or the conductivity in the normal state on the one hand and the sensitivity of Tc to disorder on the other.