Quantum phase transition in one dimensional extended Kondo lattice model away from half filling

TL;DR

This paper investigates a one-dimensional extended Kondo lattice model away from half filling, revealing a Kondo-driven quantum phase transition from a spin-gapped phase to a critical state in the localized spins.

Contribution

It introduces an effective field theory incorporating holons and spinons interacting via gauge fluctuations, highlighting the impact of Kondo hybridization on spin excitations and phase transitions.

Findings

Kondo hybridization suppresses gauge fluctuations and Berry phase effects.

A phase transition occurs when Kondo hybridization exceeds a critical value.

The localized spin chain becomes critical due to Kondo interactions.

Abstract

We study one dimensional {\it extended} Kondo lattice model, described by the $t-J$ Hamiltonian for conduction electrons away from half filling and the Heisenberg Hamiltonian for localized spins at half filling. Following Shankar,\cite{Shankar} we find an effective field theory for this model, where doped holes are represented by massless Dirac fermions (holons) and spin excitations are fractionalized into relativistic bosons (spinons). These holons and spinons interact via U(1) gauge fluctuations. Effects of Berry phase to the localized spins disappear due to the presence of Kondo couplings, causing the spinon excitations gapped. Furthermore, the gauge fluctuations are suppressed by hole doping. As a result, massive spinons are deconfined to arise in the localized spins unless the Kondo hybridization is strong enough. When the Kondo hybridization strength exceeds a certain value, we find that the localized spin chain becomes critical. This indicates that the present one dimensional Kondo lattice model exhibits a phase transition from a spin-gapped phase to a critical state in the localized spin chain, driven by the Kondo interaction.