A thermally driven out-of-equilibrium two-impurity Kondo system

TL;DR

This paper explores how thermal biases influence the nonlinear thermal and thermoelectric responses of a two-impurity Kondo system, revealing thermal diode behavior, sign reversal of thermoelectric current, and effects on Kondo-antiferromagnetic crossover.

Contribution

It demonstrates the emergence of negative differential thermal conductance and thermoelectric current sign reversal in a thermal bias-driven two-impurity Kondo system, using slave-boson formulation.

Findings

Identification of thermal diode behavior due to Kondo correlations.

Observation of thermoelectric current sign reversal controlled by system parameters.

Analysis of how thermal bias affects the Kondo-to-antiferromagnetic crossover.

Abstract

The archetypal two-impurity Kondo problem in a serially-coupled double quantum dot is investigated in the presence of a thermal bias $\theta$. The slave-boson formulation is employed to obtain the nonlinear thermal and thermoelectrical responses. When the Kondo correlations prevail over the antiferromagnetic coupling $J$ between dot spins we demonstrate that the setup shows negative differential thermal conductance regions behaving as a thermal diode. Besides, we report a sign reversal of the thermoelectric current $I(\theta)$ controlled by $t/\Gamma$ ($t$ and $\Gamma$ denote the interdot tunnel and reservoir-dot tunnel couplings, respectively) and $\theta$. All these features are attributed to the fact that at large $\theta$, both $Q(\theta)$ (heat current) and $I(\theta)$ are suppressed regardless the value of $t/\Gamma$ because the double dot decouples at high thermal biases. Eventually, and for a finite $J$, we investigate how the Kondo-to-antiferromagnetic crossover is altered by $\theta$.