Thermoelectric power of inhomogeneous superconductors: a new kind of percolation

Abstract

A theoretical analysis of a recent observation of vanishing thermopower at the superconducting transition temperature on some samples containing a minute fraction of superconductor is presented. An argument due to Jha, Reddy, and Sharma which demonstrates that the percolation threshold for thermoelectric power can be much smaller than the usual percolation threshold for conductance is analyzed. It is argued that a nonzero percolation threshold for thermoelectric power is essentially a finite-size effect, in which the size exponent is so small that for macroscopic samples of interest the threshold is more or less size independent.