Orbital caloritronic transport in strongly interacting quantum dots

TL;DR

This paper investigates thermoelectric effects in quantum dots with orbital degrees of freedom, revealing how thermal gradients induce orbital biases and how these effects can probe different Kondo regimes.

Contribution

It introduces an orbital Seebeck coefficient to characterize thermoelectric orbital effects and demonstrates its effectiveness in distinguishing SU(4) and SU(2) Kondo physics in strongly interacting quantum dots.

Findings

Orbital thermopower effectively indicates the transition between SU(4) and SU(2) Kondo regimes.

Thermoelectric orbital effects are generic in nanostructures with pseudospin.

Numerical renormalization group confirms the orbital Seebeck coefficient as a diagnostic tool.

Abstract

We discuss out-of-equilibrium population imbalances between different orbital states due to applied thermal gradients. This purely thermoelectric orbital effect appears quite generically in nanostructures with a pseudospin degree of freedom. We establish an orbital Seebeck coefficient that characterizes the induced orbital bias in response to a temperature difference between reservoirs coupled to a quantum conductor. We analyze a two-terminal strongly interacting quantum dot with two orbital states and find that the orbital thermopower acts as an excellent tool to describe the transition between SU(4) and SU(2) Kondo physics. Our conclusions are reinforced from a detailed comparison with the charge thermopower using numerical renormalization group calculations.