Competition between Kondo effect and RKKY interaction: A molecular model

Abstract

The competition between Kondo effect and RKKY interaction is studied within an exactly solvable model, obtained from the two-impurity Anderson model by replacing the conduction band by two states. Results depend on the ratio between hopping t and Kondo temperature T K: for t ⪡ T K two independent Kondo singlets are formed, while for t ⪢ T K the impurity spins have strong antiferromagnetic correlations. Extrapolation to the full Anderson model suggests that an energy scale different from the RKKY coupling is responsible for the development of magnetic correlations between Kondo singlets.