Electric and Magnetic Properties of Higher-Spin Kondo-Heisenberg Models at Strong Coupling

TL;DR

This paper explores the phase diagram of higher-spin Kondo-Heisenberg models in one dimension, revealing insulating and ferromagnetic phases, and uses analytical and numerical methods to analyze their properties at strong coupling.

Contribution

It introduces a comprehensive analysis of higher-spin ($S \\geq 1$) Kondo-Heisenberg models, including strong-coupling expansion and DMRG simulations, highlighting new phase behaviors.

Findings

Insulating phase at half-filling with parity-dependent magnetic correlations

Dominance of ferromagnetic metallic phase at generic fillings

Collapse of ferromagnetism via dimerized insulating phase at quarter-filling

Abstract

We study higher-spin ($S \geq 1$) generalization of the one-dimensional Kondo-Heisenberg model, in which the local spin-$S$ moments of the Kondo lattice model interact with each other via the antiferromagnetic Heisenberg interaction ($J_{\text{H}}$), by analytical and numerical methods. The strong-coupling (i.e., large Kondo-coupling) expansion maps out an insulating phase at half-filling whose magnetic correlation depends on the parity of $2S$ as well as a ferromagnetic metallic phase which dominates the strong-coupling region at generic fillings. Then, we carried out the Density-Matrix Renormalization Group (DMRG) simulations for $S=1$ to closely investigate the phase structure at large but finite Kondo coupling. At half-filling, the Kondo coupling and $J_{\text{H}}$ do not compete and the insulating spin-gapless phase is stable, while the competition of the two leads to a stepwise collapse of the strong-coupling ferromagnetism via an intervening dimerized insulating phase with power-law spin correlation at quarter-filling.