Critical Theory of the Two-Channel Anderson Impurity Model

TL;DR

This paper develops a boundary conformal field theory framework for the two-channel Anderson impurity model, revealing a line of stable fixed points, exact thermodynamic properties, and critical exponents, enhancing understanding of impurity behavior in mixed-valent regimes.

Contribution

It introduces a boundary conformal field theory approach combined with Bethe Ansatz to fully describe the low-energy dynamics and critical phenomena of the two-channel Anderson impurity model.

Findings

Identifies a line of stable fixed points parameterized by impurity charge valence.

Calculates exact zero-temperature entropy and impurity thermodynamics.

Derives critical exponents for Fermi edge singularities.

Abstract

We construct the boundary conformal field theory that describes the low-temperature behavior of the two-channel Anderson impurity model. The presence of an exactly marginal operator is shown to generate a line of stable fixed points parameterized by the charge valence of the impurity. We calculate the exact zero-temperature entropy and impurity thermodynamics along the fixed line. We also derive the critical exponents of the characteristic Fermi edge singularities caused by time-dependent hybridization between conduction electrons and impurity. Our results suggest that in the mixed-valent regime the electrons participate in two competing processes, leading to frustrated screening of spin and channel degrees of freedom. By combining the boundary conformal field theory with the Bethe Ansatz solution we obtain a complete description of the low-energy dynamics of the model.