Disordered Kondo nanoclusters: Effect of energy spacing

Exact-diagonalization results for Kondo nanoclusters alloyed with mixed-valence impurities show that tuning the energy spacing Δ drives the system from the Kondo to the Ruderman-Kittel-Kasuya-Yosida (RKKY) regime. The interplay of Δ and disorder gives rise to a Δ versus concentration T=0 phase diagram very rich in structure. The parity of the total number of electrons alters the competition between the Kondo and RKKY correlations. The local Kondo temperatures T_K and RKKY interactions depend strongly on the local environment and overall are enhanced by disorder, in contrast to the hypothesis of “Kondo disorder” single-impurity models.