Thermal interplay between magnetic Kondo impurities

The Kondo effect is a paradigmatic example of a many-body system in condensed matter physics. This effect appears when an electron in a localized state interacts with the conduction electrons of a metal at low temperatures. Such transitions lead to spin-flips of the electron in the localized state yielding dramatic consequences in the local density of states and the quantum transport. This emergent property allows us to classify the Kondo effect as a complex phenomenon.

When two Kondo impurities are connected via a tunneling barrier a new antiferromagnetic interaction arises: the superexchange interaction. A competition appears between the Kondo phase and the antiferromagnetic (Neel) phase.

The goal of this seminar is to provide a general overview of the Kondo effect for single- and two-impurity systems with a final discussion on the thermal and thermoelectric effects of two serially-coupled Kondo impurities. By studying the parameters of the Kondo resonances we will find different regimes depending on the interdot tunnel coupling. These regimes will be also noticeable in the thermoelectric transport yielding different behaviors in the thermocurrent. Importantly, we find strong nonlinearities in the thermal transport. Finally, we show how the thermal bias alters the crossover between the Kondo and the antiferromagnetic phase.

Reference: Miguel A. Sierra, Rosa López and Jon Soo Lim, Physical Review Letters121, 096801 (2018).