Thermally Driven Out-of-Equilibrium Two-Impurity Kondo System

Abstract

The archetypal two-impurity Kondo problem in a serially coupled double quantum dot is investigated in the presence of a thermal bias θ. 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. In addition, we report a sign reversal of the thermoelectric current I(θ) controlled by t/Γ (t and Γ denote the interdot tunnel and reservoir-dot tunnel couplings, respectively) and θ. All these features are attributed to the fact that at large θ both Q(θ) (heat current) and I(θ) are suppressed regardless of the value of t/Γ because the double dot decouples at high thermal biases. Finally, for a finite J, we investigate how the Kondo-to-antiferromagnetic crossover is altered by θ.