Mixed electrical-heat noise spectrum in a quantum dot

TL;DR

This paper investigates the mixed electrical-heat noise spectrum in a quantum dot using Keldysh Green functions, revealing its relation to thermoelectric properties and how temperature gradients affect spectral coherence.

Contribution

It provides a theoretical analysis of mixed noise in quantum dots, linking it to thermoelectric conductance and exploring the effects of temperature gradients on spectral coherence.

Findings

Mixed noise relates to thermoelectric ac-conductance at equilibrium.

Spectral coherence depends on electrical and heat current correlations.

Temperature gradients modify spectral coherence significantly.

Abstract

Using the Keldysh Green function technique, we calculate the finite-frequency correlator between the electrical current and the heat current flowing through a quantum dot connected to reservoirs. At equilibrium, we find that this quantity, called mixed noise, is linked to the thermoelectric ac-conductance by the fluctuation-dissipation theorem. Out-of-equilibrium, we discuss its spectrum and find evidence of the close relationship between the mixed noise and the thermopower. We study the spectral coherence and identify the conditions to have a strong correlation between the electrical and heat currents. The change in the spectral coherence due to the presence of a temperature gradient between the reservoirs is also highlighted.