Universal Thermal Entanglement of Multichannel Kondo Effects

TL;DR

This paper introduces a method to analyze thermal entanglement in multichannel Kondo effects using boundary conformal field theory, revealing universal decay behavior and quantum coherence properties.

Contribution

It develops a novel approach combining entanglement negativity and BCFT to study thermal entanglement in impurity problems, providing analytical and numerical insights.

Findings

Zero-temperature entanglement is maximal regardless of channels.

Entanglement decays as a power law at low temperatures.

Decay exponent relates to BCFT boundary operator scaling dimension.

Abstract

Quantum entanglement between an impurity and its environment is expected to be central in quantum impurity problems. We develop a method to compute the entanglement in spin-1/2 impurity problems, based on the entanglement negativity and the boundary conformal field theory (BCFT). Using the method, we study the thermal decay of the entanglement in the multichannel Kondo effects. At zero temperature, the entanglement has the maximal value independent of the number of the screening channels. At low temperature, the entanglement exhibits a power-law thermal decay. The power-law exponent equals two times of the scaling dimension of the BCFT boundary operator describing the impurity spin, and it is attributed to the energy-dependent scaling behavior of the entanglement in energy eigenstates. These agree with numerical renormalization group results, unveiling quantum coherence inside the Kondo screening length.