Seminar Talk of Dr. Krzysztof Wójcik (Institute of Molecular Physics Polish Academy of Science)

The phase diagram of the conventional 2-impurity Kondo model and its relevance to correlated lattice models have been a subject of a long debate. It is now clear that it features a quantum phase transition (QPT) between the Kondo and the RKKY phase only in the model extended with a specially designed counter-term. I will present results obtained for a different extension of the standard 2-impurity model, where each of the impurities is coupled to a different host, and the hosts (not impurities) are directly coupled by spin-spin exchange. The model exhibits Jones-Varma QPT even away from the particle-hole symmetry point. Moreover, a second QPT occurs upon tuning the same inter-host coupling to very high values, where the system forms 2-impurity version of a spin-liquid. I will discuss the possibilities for realization of this scenario in quantum-dot structures and heavy-fermion materials.

Host: Frithjof B. Anders