Tunable Doniach phase diagram for strongly-correlated nanoclusters

Exact diagonalization calculations reveal that the energy spacing D in the conduction band tunes the interplay between the local Kondo and nonlocal Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions, giving rise to a Doniach phase diagram for a nanocluster with regions of prevailing Kondo or RKKY correlations. The parity of the total number of electrons alters the competition between the Kondo and RKKY correlations. This interplay may be relevant to experimental realizations of small rings or quantum dots with tunable magnetic properties. Below a critical value Vc of the hybridization the susceptibility exhibits a low-T exponential activation behavior determined by the interplay of the spin gap and D.