Kondo effect in two-dimensional disordered electron systems

In disordered systems, the localization effect of the conduction electron enhances the electron correlation effects drastically, leading to conspicuous features particularly in low-dimensional systems. The Kondo effect is a typical phenomenon caused by the electron correlation around a magnetic impurity. Using perturbative expansion, the Kondo effect in the weakly localized regime was investigated. It was shown that the Kondo logarithmic terms are modified into the product of new anomalous terms and the Kondo logarithmic ones, and that the latters are scaled into the same Kondo temperature as that without randomness. The Kondo effect in strongly disordered systems was studied by taking account of the Coulomb interaction among conduction electrons. It was shown that the Kondo temperature has a spatial distribution, which leads to divergence behaviors of physical quantities as temperature approaches zero. Such a spatial distribution in the Kondo temperature was suggested from experimental results of strong broadening of the Cu NMR line of UCu5−xPdx. 10) In spite of these findings, the effects of strong randomness itself on the behavior of a magnetic impurity have not yet been fully investigated from a microscopic viewpoint. In this paper, we study the Kondo effect in twodimensional (2D) strongly disordered electron systems using a finite-temperature quantum Monte Carlo (QMC) method. Let us consider the single-impurity Anderson model with on-site random potentials described by the Hamiltonian