Low-temperature properties of small heavy fermion particles

Abstract

Heavy fermions arise from the hybridization of extended conduction states with strongly correlated localized f states. Depending on the position of the Fermi level the system can be metallic or semiconducting. In nanosized particles the extended states have discrete energies and their energy spacing competes with TK. We consider a small Kondo insulator particle described by the symmetric Anderson model within the mean-field slave-boson approximation at low T. The formation of a ferromagnetic ground state is prevented for small system sizes. The susceptibility, entropy, and specific heat are thermally activated at low T with a gap of the order of TK for the insulator, but only of the order of spTK/D in the metallic case, where sp is the mean energy level spacing.