Kondo-stabilized spin-liquid phase of 2 impurities

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 it features Jones-Varma quantum phase transition (QPT) between the Kondo and the RKKY phase, which is unstable against particle-hole asymmetry. I will present results obtained for a modified 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. Even more importantly, a second QPT occurs upon tuning the same inter-host coupling to even higher values, where the system forms 2-impurity version of a spin-liquid, defined as a state with large, but not complete spin-spin correlations and non-universal impurity spectral density. I will discuss the possibilities for realization of this scenario in quantum-dot structures and heavy-fermion materials.