Nonlinear Thermoelectric Response of Quantum Dots: Renormalized Dual Fermions Out of Equilibrium

Abstract

The thermoelectric transport properties of nanostructured devices continue to attract attention from theorists and experimentalist alike as the spatial confinement allows for a controlled approach to transport properties of correlated matter. Most of the existing work, however, focuses on thermoelectric transport in the linear regime despite the fact that the nonlinear conductance of correlated quantum dots has been studied in some detail throughout the last decade. Here, we review our recent work on the effect of particle-hole asymmetry on the nonlinear transport properties in the vicinity of the strong coupling limit of Kondo-correlated quantum dots and extend the underlying method, a renormalized superperturbation theory on the Keldysh contour, to the thermal conductance in the nonlinear regime. We determine the charge, energy, and heat current through the nanostructure and study the nonlinear transport coefficients, the entropy production, and the fate of the Wiedemann-Franz law in the non-thermal steady-state. Our approach is based on a renormalized perturbation theory in terms of dual fermions around the particle-hole symmetric strong-coupling limit.

Thermoelectric response of a correlated impurity in the nonequilibrium Kondo regime

“…(12) above 72,99 . Notice that, in contrast to the particle and energy current, the nonequilibrium heat current is not conserved and the left and right contributions differ 99 .…”

“…While the electronic transport has been studied extensively, the thermoelectric transport theory mostly focused on the linear response regime 13,25,[71][72][73][74][75][76][77][78][79][80][81][82][83][84][85][86][87][88][89] . The nonlinear regime has been addressed mainly in the weak coupling limit 32,78,[90][91][92][93][94][95][96][97] , a systematic analysis including renormalization effects 66,67,98,99 beyond the perturbative regime is still missing. Recent findings 90,99 indicate a Seebeck coefficient which is enhanced with respect to the equilibrium result.…”

“…The nonlinear regime has been addressed mainly in the weak coupling limit 32,78,[90][91][92][93][94][95][96][97] , a systematic analysis including renormalization effects 66,67,98,99 beyond the perturbative regime is still missing. Recent findings 90,99 indicate a Seebeck coefficient which is enhanced with respect to the equilibrium result. A possible key to this observation are the different relaxation processes occurring at finite temperature and bias voltage.…”

Nonequilibrium distribution functions for quantum transport: Universality and approximation for the steady state regime

“…Then all quantities, GFs and self-energies, follow the statistics given by the non-interacting case, as suggested in Ref. [57]. However this is generally not true.…”

Fate of the spin- 12 Kondo effect in the presence of temperature gradients

“…Most of them are focused on the study of the Seebeck coefficient S = V th θ employing a large variety of methods: nonperturbative resonant tunneling approximation [21], second-order perturbation theory for the onsite Coulomb interaction [22], slave-boson noncrossing approximation (NCA) [23], generalized Keldyshbased NCA [24], nonequilibrium Green's functions beyond Hartree-Fock [25], quantum [26] and auxiliary [27] master equation approaches and dual fermions renormalized perturbation theory [28]. In the linear regime, experimental evidence of the influence of the Kondo effect in the thermopower of a QD was reported in Ref.…”