Superconducting fluctuations and the Nernst effect: A diagrammatic approach

TL;DR

This paper provides a microscopic calculation of superconducting fluctuations' contribution to the Nernst effect near the critical temperature, confirming previous results and clarifying the dominant fluctuation mechanisms.

Contribution

It offers a diagrammatic derivation within BCS theory for the fluctuation contribution to the Nernst effect, emphasizing the dominance of Aslamazov-Larkin diagrams near T_c.

Findings

Aslamazov-Larkin diagrams dominate near T_c

Microscopic results match stochastic Ginzburg-Landau predictions

Other fluctuation contributions are less divergent as T approaches T_c

Abstract

We calculate the contribution of superconducting fluctuations above the critical temperature $T_c$ to the transverse thermoelectric response $\alpha_{xy}$, the quantity central to the analysis of the Nernst effect. The calculation is carried out within the microscopic picture of BCS, and to linear order in magnetic field. We find that as $T \to T_c$, the dominant contribution to $\alpha_{xy}$ arises from the Aslamazov-Larkin diagrams, and is equal to the result previously obtained from a stochastic time-dependent Ginzburg-Landau equation [Ussishkin, Sondhi, and Huse, arXiv:cond-mat/0204484]. We present an argument which establishes this correspondence for the heat current. Other microscopic contributions, which generalize the Maki-Thompson and density of states terms for the conductivity, are less divergent as $T \to T_c$.