Orbital caloritronic transport in strongly interacting quantum dots

We investigate spin-dependent thermoelectric transport through a system of two coupled quantum dots attached to reservoirs of spin-polarized electrons. Generally, we focus on the strongly correlated regime of transport. To this end, a slave-boson method for finite U is employed. Our main goal is to show that, apart from complex low-temperature physics, such a basic multilevel system provides a possibility to examine various quantum interference effects, with particular emphasis put on the influence of such phenomena on thermoelectric transport. Apart from the influence of interference effects on spin-degenerate charge transport, we show how spin-dependent transport, induced by ferromagnetic leads, can be modified as well. Finally, we also consider the case where the spin-relaxation time in the ferromagnetic leads is relatively long, which leads to the so-called spin thermoelectric effects.

Section: Introductionmentioning

confidence: 99%

Spin-dependent thermoelectric effects in a strongly correlated double quantum dot

Karwacki¹,

Trocha²

2016

“…The paradigmatic SU(4) Kondo physics has been experimentally studied in CNTs [12,[19][20][21][22][23], double QDs [24] and single-atom transistor [25]. Various theoretical works [26][27][28][29][30][31] have contributed towards better understanding of SU(4) Kondo physics over past years. In addition, exciting proposals have been put forth for the experimental realization of different variants of SU(N ) Kondo systems.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear Seebeck effect of SU(N) Kondo impurity

Karki

Kiselev

2019

We develop a theoretical framework to study the influences of coupling asymmetry on the thermoelectrics of a strongly coupled SU(N ) Kondo impurity based on a local Fermi liquid theory. Applying non-equilibrium Keldysh formalism, we investigate charge current driven by the voltage bias and temperature gradient in the strong coupling regime of an asymmetrically coupled SU(N ) quantum impurity. The thermoelectric characterizations are made via non-linear Seebeck effects. We demonstrate that the beyond particle-hole (PH) symmetric SU(N ) Kondo variants are highly desirable with respect to the corresponding PH symmetric setups in order to have significantly improved thermoelectric performance. The greatly enhanced Seebeck coefficients by tailoring the coupling asymmetry of beyond PH symmetric SU(N ) Kondo effects are explored. Apart from presenting the analytical expressions of asymmetry dependent transport coefficients for general SU(N ) Kondo effects, we make a close connection of our findings with the experimentally studied SU(2) and SU(4) Kondo effects in quantum dot nano structures. Seebeck effects associated with the theoretically proposed SU(3) Kondo effects are discussed in detail. arXiv:1908.00415v1 [cond-mat.mes-hall]

“…[41]. Finally, we briefly mention exciting topics where thermoelectrics in Kondo artificial impurities play a significant role: relaxation dynamics [42], orbital degrees of freedom [43,44], universal ac thermopower [45], hybrid devices connected to ferromagnetic and superconducting leads [46], assisted hopping [47] and different configurations such as parallel [48] or side coupled double QDs [49].…”

Section: Introductionmentioning

confidence: 99%

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

Sierra¹,

López²,

Sánchez³

2017

Self Cite

We consider a strongly interacting quantum dot connected to two leads held at quite different temperatures. Our aim is to study the behavior of the Kondo effect in the presence of large thermal biases. We use three different approaches, namely, a perturbation formalism based on the Kondo Hamiltonian, a slave-boson mean-field theory for the Anderson model at large charging energies and a truncated equation-of-motion approach beyond the Hartree-Fock approximation. The two former formalisms yield a suppression of the Kondo peak for thermal gradients above the Kondo temperature, showing a remarkably good agreement despite their different ranges of validity. The third technique allows us to analyze the full density of states within a wide range of energies. Additionally, we have investigated the quantum transport properties (electric current and thermocurrent) beyond linear response. In the voltage-driven case, we reproduce the split differential conductance due to the presence of different electrochemical potentials. In the temperature-driven case, we observe a strongly nonlinear thermocurrent as a function of the applied thermal gradient. Depending on the parameters, we can find nontrivial zeros in the electric current for finite values of the temperature bias. Importantly, these thermocurrent zeros yield direct access to the system's characteristic energy scales (Kondo temperature and charging energy).