Non-linear sigma model study of magnetic dephasing in a mesoscopic spin glass

TL;DR

This paper develops a nonlinear sigma model to analyze quantum transport in mesoscopic metals with magnetic impurities in a spin glass phase, capturing the crossover between different universality classes and calculating conductance correlations.

Contribution

It introduces a novel nonlinear sigma model that incorporates magnetic and scalar potentials with correlations, describing the crossover between orthogonal and unitary classes in spin glasses.

Findings

Model describes magnetic dephasing in spin glasses.

Calculates conductance correlations between frozen spin configurations.

Shows crossover behavior between universality classes.

Abstract

We propose a nonlinear sigma model for the description of quantum transport in a mesoscopic metallic conductor with magnetic impurities frozen in a spin glass phase. It accounts for the presence of both the corresponding scalar and magnetic random potentials. In a spin glass, this magnetic random potential is correlated between different realizations. As the strength of the magnetic potential is varied, this model describes the crossover between orthogonal and unitary universality classes of the nonlinear sigma model. We apply this technique to the calculations of the correlation of conductance between two frozen spin configurations in terms of dephasing rates for the usual low energy modes of weak localization theory.