Kondo resonance assisted thermoelectric transport through strongly correlated quantum dots

Abstract

We theoretically studied the thermoelectric transport propertiesof a strongly correlated quantum dot system in the presence of the Kondo effect based on accurate numerical evaluations using the hierarchical equations of motion approach.The thermocurrent versus gate voltage shows a distinct sawtooth line-shape at high temperatures.In particular, the current changes from positive (hole charge) to negative (particle charge) inthe electron number $N~=~1$ region due to the Coulomb blockade effect. However, at low temperatures, where the Kondo effect occurs, the thermocurrents charge polarity reverses,along witha significantly enhanced magnitude.As anticipated, the current sign can be analyzed by the occupation difference between particle and hole. Moreover, the characteristic turnover temperature can be further definedat which the influences of the Coulomb blockade and Kondo resonance are in an effective balance.Remarkably, the identified characteristic turnover temperature, as a function of the Coulomb interaction and dot-lead coupling, possessed a much higher value than the Kondo temperature. When a magnetic field is applied, a spin-polarized thermocurrent can be obtained, which could be tested in future experiments.