Effective Heisenberg-Model Description of the Coupled Spin-Pseudospin Model for Quarter-Filled Ladders

TL;DR

This paper uses quantum Monte Carlo simulations to analyze a coupled spin-pseudospin model for quarter-filled ladders, revealing conditions where spin behavior mimics a 1D Heisenberg model and explaining anomalous spin dynamics in charge-ordered materials.

Contribution

It introduces an effective Heisenberg-model description for the coupled spin-pseudospin system in quarter-filled ladders, highlighting its relevance to charge-ordering phenomena.

Findings

Spin susceptibility matches 1D Heisenberg model in certain parameters.

Identifies temperature and parameter regimes with Heisenberg-like spin behavior.

Explains anomalous spin dynamics in charge-ordered $ ext{NaV}_2 ext{O}_5$.

Abstract

Quantum Monte Carlo method is used to study the coupled spin-pseudospin Hamiltonian in one-dimension (1D) that models the charge-ordering instability of the anisotropic Hubbard ladder at quarter filling. We calculate the temperature dependence of the uniform spin susceptibility and the spin and charge excitation spectra of the system to show that there is a parameter and temperature region where the spin degrees of freedom behave like a 1D antiferromagnetic Heisenberg model. Anomalous spin dynamics in the disorder phase of a typical charge-ordered material $\alpha'$-NaV$_2$O$_5$ is thereby considered.