Correlations between charge and heat currents in an interacting quantum dot

Abstract : We consider an interacting quantum dot connected to two reservoirs driven at distinct voltage/temperature and we study the correlations between charge and heat currents first as a function of the applied voltage bias, and second as a function of the temperature gradient between the two reservoirs. The Coulomb interactions in the quantum dot are treated using the Hartree approximation and the dot occupation number is determined self-consistently. The correlators exhibit structures in their voltage dependency which are highly non-linear when the coupling between the dot and the reservoirs is weak, and their behavior with temperature is non-monotonous. Moreover the sign of heat cross-correlator can change contrary to what happens with the charge cross-correlator which is always negative. The presence of Coulomb interactions enlarges the domain of voltage in which the heat cross-correlator is negative. 1. Introduction The field of quantum thermoelectricity is very active right now. Its main objectives are the increase of the thermoelectric conversion efficiency by reducing the size of the system and the possibility to build on-chip thermoelectric nanodevices. Among the recent experimental works, we can cite the measurement of non-linear thermovoltage and thermocurrent in quantum dots [1], the study of the Seebeck effect in magnetic tunnel junctions [2] and the measurement of first, second and third harmonic voltage responses in nanoscale spin valves [3]. In parallel, theoretical activities are needed. The purpose here is to understand how Coulomb interactions in the quantum dot affect the profile of the different kinds of currents correlators that one can define when both charge and heat fluxes are present, i.e., the charge/charge correlator, the heat/heat correlator as well as the mixed charge/heat correlator. This last quantity has been introduced quite recently [4] and has been considered so far only in a three-terminal thermoelectric device with two quantum dots in the Coulomb blockade regime [5]. It deserves to be studied in a more systematic way since it has been shown that it allows to quantify the thermoelectric conversion in both linear response regime and Schottky regime [6].
Keywords : quantum
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Adeline Crépieux, Paul Eyméoud, Fabienne Michelini. Correlations between charge and heat currents in an interacting quantum dot. Journal of Physics: Conference Series, IOP Publishing, 2015, J. Phys.: Conf. Ser. 592, pp.012140. ⟨10.1088/1742-6596/592/1/012140⟩. ⟨hal-01257933⟩

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