Phase dependent differential thermopower of SND junctions: Pair-breaking effects and Gaussian fluctuations

TL;DR

This paper investigates the phase-dependent thermopower in SND junctions, considering fluctuation effects and phase differences, revealing effects related to pairing symmetry and temperature differences between superconductors.

Contribution

It generalizes Ginzburg-Landau theory to include fluctuation effects and analyzes the phase-dependent thermoelectric power in SND junctions with mixed pairing symmetries.

Findings

TEP peak near / for identical superconductors

TEP proportional to T_d - T_s for different T_c superconductors

Strong phase dependence influenced by pairing symmetry and chemical imbalance

Abstract

We start with revisiting our previous results on thermoelectric response of SNS configuration in a C-shaped Bi(x)Pb(1-x)Sr(2)CaCu(2)O(y) sample in order to include strong fluctuation effects. Then, by appropriate generalization of the Ginzburg-Landau theory based on admixture of s-wave and d-wave superconductors, we consider a differential thermoelectric power (TEP) of SND junction. In addition to its strong dependence on the relative phase \theta =\phi_s-\phi_d between the two superconductors, two major effects are shown to influence the behavior of the predicted TEP. One, based on the chemical imbalance at SD interface, results in a pronounced maximum of the TEP peak near \theta =\pi /2 (where the so-called s+id mixed pairing state is formed) for two identical superconductors (with T_d=T_s\equiv T_c). Another effect, which should manifest itself at SD interface comprising an s-wave low-T_c superconductor and a d-wave high-T_c superconductor (with T_d\neq T_s), predicts S_p\propto T_d-T_s for the TEP peak value. The experimental conditions under which the predicted behavior of the induced differential TEP can be measured are discussed.