On evaluation of transverse spin fluctuations in quantum magnets

TL;DR

This paper introduces a numerical method to evaluate transverse spin correlations in quantum magnets within the random phase approximation, analyzing quantum corrections and defect effects in Hubbard antiferromagnets across various dimensions and interaction strengths.

Contribution

The paper presents a new numerical approach for calculating transverse spin fluctuations and extends it to study defect effects in Hubbard antiferromagnets, including vacancy-induced phenomena.

Findings

Quantum corrections to sublattice magnetization are evaluated across the U/t range.

Vacancy-induced enhancement of transverse spin fluctuations is observed in the infinite-U limit.

Low-U impurities suppress overall spin fluctuations but locally enhance them at impurity sites.

Abstract

A numerical method is described for evaluating transverse spin correlations in the random phase approximation. Quantum, spin-fluctuation corrections to sublattice magnetization are evaluated for the half-filled Hubbard antiferromagnet in two and three dimensions in the whole U/t range. Extension to the case of defects in the Hubbard AF is discussed, and the vacancy-induced enhancement in transverse spin fluctuation is obtained in the infinite-U limit for the spin vacancy problem in two dimensions, for vacancy concentration up to the percolation threshold. For low-U impurities, the overall spin fluctuation correction is found to be strongly suppressed, although surprisingly spin fluctuations are locally enhanced at the low-U sites.