ABCD of Kondo effect

TL;DR

This paper investigates the Kondo effect with impurities under general symmetry groups using boundary conformal field theory, analyzing thermodynamic properties and impurity behavior at low temperatures.

Contribution

It introduces the concept of the G-Kondo effect with generic symmetry groups and derives an effective 1D model to study its thermodynamics.

Findings

Impurity entropy at conformal fixed point calculated.

Low temperature specific heat and susceptibility behaviors analyzed.

Wilson ratio discussed for various symmetry groups.

Abstract

We explore the Kondo effect incorporating the localized impurity transforming under generic symmetry group $G$, that we call the $G$-Kondo effect. We derive the one-dimensional effective model coupled with the impurity, and studied the thermodynamic properties based on the boundary conformal field theory approach. We in particular study the impurity entropy at the conformal fixed point, and the low temperature behavior of the specific heat and the susceptibility. We also consider the Wilson ratio based on these results, and mention the case with exceptional group symmetry.