A 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. Besides, 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 the value of $t/Γ$ 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 $θ$.

6 pages, 5 figures