Impact of criticality and phase separation on the spin dynamics of the one-dimensional t-J model

TL;DR

This paper investigates how criticality and phase separation influence the spin dynamics in the one-dimensional t-J model, revealing significant changes in spin excitation spectra as the system transitions from free-fermion behavior to phase separation.

Contribution

It provides a detailed analysis of the evolution of spin excitations across different phases in the t-J model using the recursion method.

Findings

Dispersions and line shapes of spin excitations change significantly with exchange coupling.

Two-spinon spectrum of the Heisenberg chain appears gradually in the phase-separated state.

Major metamorphosis of spin excitation spectra observed between free-fermion and phase-separated regimes.

Abstract

The recursion method is used to determine the T=0 spin dynamic structure factor S_{zz}(q,\omega) in the Luttinger liquid state and in the phase-separated state of the one-dimensional t-J model. As the exchange coupling increases from zero, the dispersions and line shapes of the dominant spin excitations are observed to undergo a major metamorphosis between the free-fermion limit and the onset of phase separation. The familiar two-spinon spectrum of the Heisenberg antiferromagnetic chain emerges gradually in the strongly phase-separated state.