Even-odd effect in the thermopower and strongly enhanced thermoelectric efficiency for superconducting single-electron transistors

TL;DR

This paper investigates how the parity effect influences thermopower in superconducting single-electron transistors, revealing significant enhancements in thermoelectric efficiency under certain conditions.

Contribution

It provides a detailed analysis of the parity effect on thermopower and thermoelectric efficiency in NSN single-electron transistors using realistic device parameters.

Findings

Thermopower depends strongly on the superconducting gap Δ.

Parity regime shows a dramatic increase in thermoelectric figure of merit ZT.

Enhanced ZT can be explained through transport energy averages and variances.

Abstract

It is well known that the transport properties of single-electron transistors with a superconducting island and normal-conducting leads (NSN SET) may depend on whether or not there is a single quasiparticle on the island. This parity effect has pronounced consequences for the linear transport properties. Here we analyze the thermopower of NSN SET with and without parity effect, for entirely realistic values of device parameters. Besides a marked dependence of the thermopower on the superconducting gap $\Delta$ we observe an enhancement in the parity regime which is accompanied by a dramatic increase of the thermoelectric figure of merit ZT. The latter can be explained within a simple re-interpretation of ZT in terms of averages and variances of transport energies.