Quantum-fluctuation effects on the thermopower of a single-electron transistor

TL;DR

This paper investigates how quantum fluctuations influence the thermopower and thermal conductance of a single-electron transistor, revealing logarithmic temperature dependencies linked to Kondo correlations.

Contribution

It introduces a combined perturbative and non-perturbative approach to analyze quantum fluctuation effects beyond weak tunneling in single-electron transistors.

Findings

Quantum fluctuations cause a logarithmic reduction of the Coulomb-blockade gap.

Thermopower reflects the energy shift due to quantum fluctuations.

The study identifies renormalization effects associated with many-channel Kondo correlations.

Abstract

We study thermal conductance and thermopower of a metallic single-electron transistor beyond the limit of weak tunnel coupling. Employing both a systematic second-order perturbation expansion and a non-perturbative approximation scheme, we find, in addition to sequential and cotunneling contributions, terms that are associated with the renormalization of system parameters due to quantum fluctuations. The latter can be identified by their logarithmic temperature dependence that is typical for many-channel Kondo correlations. In particular, the temperature dependence of thermopower, which provides a direct measure of the average energy of transported particles, reflects the logarithmic reduction of the Coulomb-blockade gap due to quantum fluctuations.