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Chapter 7 Superconductivity above the Transition Temperature

Elsevier Science & Technology
DOI: 10.1016/s0079-6417(08)60066-9
  • Physics


Publisher Summary The aim of this chapter is to present the evidence indicating that the rounding of the transition curve observed for thin samples having short electron mean free paths is an intrinsic effect. In the best cases, influences of sample inhomogeneity can be almost completely eliminated. Comparison of experiments with theory gives strong grounds for believing that the temperature dependent conductance observed above the transition temperature is due to a sort of fluctuation superconductivity. Superconducting carriers formed at temperatures above Tc as a result of thermodynamic fluctuations have a finite lifetime, in which they can be accelerated by an externally applied electric field. Such carriers in addition to contributing to the conductivity would be expected to influence a whole series of other properties of a superconductor above the transition temperature. Two such effects have in fact been observed. Theories based on the idea of superconducting carriers being produced above the transition temperature as a result of thermal fluctuations give a satisfactory account of the observed para conductivity. On the microscopic level the extra carriers are pictured as Cooper pairs able to move freely through the material during a finite lifetime.

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