Free Magnetic Moments in Disordered Metals

TL;DR

This paper investigates how nonmagnetic disorder in metals affects the Kondo effect, revealing that disorder can suppress magnetic screening and lead to a higher probability of unscreened magnetic moments at low temperatures.

Contribution

It provides numerical and analytical evidence that disorder alters the distribution of Kondo temperatures, challenging previous assumptions based on random matrix theory.

Findings

Disorder causes a second peak at low Kondo temperatures.

Probability of unscreened moments increases with disorder.

Distribution of Kondo temperatures broadens in the thermodynamic limit.

Abstract

The screening of magnetic moments in metals, the Kondo effect, is found to be quenched with a finite probability in the presence of nonmagnetic disorder. Numerical results for a disordered electron system show that the distribution of Kondo temperatures deviates strongly from the result expected from random matrix theory. A pronounced second peak emerges for small Kondo temperatures, showing that the probability that magnetic moments remain unscreened at low temperatures increases with disorder. Analytical calculations, taking into account correlations between eigenfunction intensities yield a finite width for the distribution in the thermodynamic limit. Experimental consequences for disordered mesoscopic metals are discussed.