Thermoelectric effects in Kondo-correlated quantum dots

Abstract

PACS. 72.20.Pa -Thermoelectric and thermomagnetic effects. PACS. 72.15.Qm -Scattering mechanisms and Kondo effect. PACS. 73.23.Hk -Coulomb blockade; single-electron tunneling.Abstract. -In this Letter we study thermoelectric effects in ultra small quantum dots. We study the behaviour of the thermopower, Peltier coefficient and thermal conductance both in the sequencial tunneling regime and in the regime where Kondo correlations develope. Both cases of linear response and non-equilibrium induced by strong temperature gradients are considered. The thermopower is a very sensitive tool to detect Kondo correlations. It changes sign both as a function of temperature and temperature gradient. We also discuss violations of the Wiedemann-Franz law.

Thermoelectric phenomena in a quantum dot asymmetrically coupled to external leads

“…This law describes transport in Fermi liquid bulk metals and in general is not obeyed in QD systems where the transport takes place through a small confined region [21,22,24]. However, at very low temperatures, where the Kondo effect develops and the ground state of the system has Fermi liquid nature, the WF law is recovered.…”

“…1 we show the temperature dependence of the (δ independent) thermopower calculated from kinetic coefficients L ij (solid line) and compare it to that obtained from so called Mott formula [38] (dashed line). Thermopower is very useful measure of the Kondo correlations [21,22,24,39]. Below the Kondo temperature T K it is negative, indicating particle like transport and changes sign at higher temperatures, where the transport is hole-like.…”

“…Here we present a more systematic study on the role of the asymmetry in the couplings to the leads in thermoelectric and transport properties of quantum dot system. Thermoelectric properties (thermopower and thermal conductance) in the Kondo regime have already been investigated in the quantum dots coupled to the normal [21,22,23] and the ferromagnetic [24,25] leads, however the role of the asymmetry in the couplings has not been discussed so far. Thus we shall concentrate on the conductance, thermal conductance, thermopower and related quantities such as thermoelectric figure of merit which directly provides the information on the usefulness of the system for applications and Wiedemann-Franz ratio which signals breakdown of the Fermi liquid state when its normalized value differs from 1.…”

Thermoelectric effects in strongly interacting quantum dot coupled to ferromagnetic leads

“…Thermal properties (thermopower and thermal conductance) of the quantum dot coupled to the normal leads in the Kondo regime have recently been investigated [32]- [34]. Thermopower has been shown to be very sensitive and powerful tool to study the Kondo effect.…”

Scattering theory of thermocurrent in quantum dots and molecules

“…Therefore, relatively large in magnitude thermocurrent flowing through a system may indicate that the system operates in the regime favorable for energy conversion [20]. Properties of the thermovoltage in molecular junctions and quantum dots were theoretically analyzed in numerous works [20][21][22][23][24][25][26][27][28][29]. As yet, less attention was paid to studies of thermocurrent in spite of the fact that I th is more straightforward to measure and model than V th , as stated in the recent work [19].…”