Quantum Phase Transition and Protected Ideal Transport in a Kondo Chain

TL;DR

This paper investigates a one-dimensional Kondo chain with anisotropic interactions, revealing a quantum phase transition that leads to a phase with protected transport akin to topological insulators, and another phase with spin-charge separation.

Contribution

It introduces a detailed analysis of anisotropic Kondo chains showing a quantum phase transition and identifies a phase with symmetry-protected transport similar to topological insulators.

Findings

Easy plane anisotropy phase exhibits symmetry-protected transport.

Easy axis anisotropy phase shows spin-charge separation with unprotected modes.

Quantum phase transition separates two distinct low-energy phases.

Abstract

We study the low energy physics of a Kondo chain where electrons from a one-dimensional band interact with magnetic moments via an anisotropic exchange interaction. It is demonstrated that the anisotropy gives rise to two different phases which are separated by a quantum phase transition. In the phase with easy plane anisotropy, Z$_2$ symmetry between sectors with different helicity of the electrons is broken. As a result, localization effects are suppressed and the dc transport acquires (partial) symmetry protection. This effect is similar to the protection of the edge transport in time-reversal invariant topological insulators. The phase with easy axis anisotropy corresponds to the Tomonaga-Luttinger liquid with a pronounced spin-charge separation. The slow charge density wave modes have no protection against localizatioin.