Thermoelectric response of a correlated impurity in the nonequilibrium Kondo regime

TL;DR

This paper investigates how a correlated impurity's thermoelectric response behaves under nonequilibrium conditions in the Kondo regime, revealing qualitative differences from electric conductance and implications for nanoscale temperature sensing.

Contribution

It provides a detailed analysis of the thermoelectric response in the nonequilibrium Kondo regime, highlighting differences from electric conductance and connecting spectral function behavior to thermoelectric effects.

Findings

Thermoelectric response differs qualitatively from electric conductance under bias and temperature.

Asymmetric suppression or enhancement of split Kondo peaks explains thermoelectric behavior.

Results suggest potential for quantum dot devices as nanoscale temperature sensors.

Abstract

We study nonequilibrium thermoelectric transport properties of a correlated impurity connected to two leads for temperatures below the Kondo scale. At finite bias, for which a current flows across the leads, we investigate the differential response of the current to a temperature gradient. In particular, we compare the influence of a bias voltage and of a finite temperature on this thermoelectric response. This is of interest from a fundamental point of view to better understand the two different decoherence mechanisms produced by a bias voltage and by temperature. Our results show that in this respect the thermoelectric response behaves differently from the electric conductance. In particular, while the latter displays a similar qualitative behavior as a function of voltage and temperature, both in theoretical and experimental investigations, qualitative differences occur in the case of the thermoelectric response. In order to understand this effect, we analyze the different contributions in connection to the behavior of the impurity spectral function versus temperature. Especially in the regime of strong interactions and large enough bias voltages we obtain a simple picture based on the asymmetric suppression or enhancement of the split Kondo peaks as a function of the temperature gradient. Besides the academic interest, these studies could additionally provide valuable information to assess the applicability of quantum dot devices as responsive nanoscale temperature sensors.