Negativity as the Entanglement Measure to Probe the Kondo Regime in the Spin-Chain Kondo Model

TL;DR

This paper uses negativity, a quantum information measure, to analyze the entanglement structure in a spin chain Kondo model, revealing the spatial extent of the Kondo cloud and distinguishing it from gapped regimes.

Contribution

It introduces negativity as a true entanglement measure to characterize the Kondo regime and ground state properties in a spin chain model, providing new insights into non-perturbative regimes.

Findings

Negativity effectively characterizes the Kondo screening cloud.

Impurity spin is maximally entangled with the Kondo cloud.

Distinct entanglement features differentiate gapless and gapped regimes.

Abstract

We study the entanglement of an impurity at one end of a spin chain with a block of spins using negativity as a true measure of entanglement to characterize the unique features of the gapless Kondo regime in the spin chain Kondo model. For this spin chain in the Kondo regime we determine- with a true entanglement measure- the spatial extent of the Kondo screening cloud, we propose an ansatz for its ground state and demonstrate that the impurity spin is indeed maximally entangled with the cloud. To better evidence the peculiarities of the Kondo regime, we carry a parallel analysis of the entanglement properties of the Kondo spin chain model in the gapped dimerised regime. Our study shows how a genuine entanglement measure stemming from quantum information theory can fully characterize also non perturbative regimes accessible to certain condensed matter systems.