Eur. Phys. J. B 11, 5-11 (1999)
https://doi.org/10.1007/s100510050911

On evaluation of transverse spin fluctuations in quantum magnets

Department of Physics, Indian Institute of Technology, Kanpur-208016, India

Corresponding author: ^a avinas@iitk.ac.in

Received: 27 April 1998
Revised: 13 August 1998
Published online: 15 September 1999

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 antiferromagnetic ground state of the half-filled Hubbard model in two and three dimensions in the whole U/t range. Extension to the case of defects in the AF is also discussed for spin vacancies and low-U impurities. In the U/t->∞ limit, the vacancy-induced enhancement in the spin fluctuation correction is obtained 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.