Mutual information, quantum phase transition, and phase coherence in Kondo systems

TL;DR

This paper introduces a new static auxiliary field approximation to study Kondo systems, revealing the role of hybridization fluctuations and mutual information in understanding quantum phase transitions and phase coherence.

Contribution

The paper develops a sign-problem-free method that captures spatial hybridization fluctuations and uses mutual information to analyze intersite correlations in Kondo systems.

Findings

Mutual information diverges logarithmically near the Varma-Jones fixed point.

Large phase mutual information indicates intersite phase coherence.

Method overcomes mean-field limitations by including spatial fluctuations.

Abstract

We propose a static auxiliary field approximation to study the hybridization physics of Kondo systems without the sign problem and use the mutual information to measure the intersite hybridization correlations. Our method takes full account of the spatial fluctuations of the hybridization fields at all orders and overcomes the artificial (first-order) phase transition predicted in the mean-field approximation. When applied to the two-impurity Kondo model, it reveals a logarithmically divergent amplitude mutual information near the so-called "Varma-Jones" fixed point and a large phase mutual information manifesting the development of intersite phase coherence in the Kondo regime, with observable influences on physical properties. These highlight the importance of hybridization fluctuations and confirm the mutual information as a useful tool to explore the hybridization physics in Kondo systems.