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arXiv:cond-mat/0010275 · Physical review. B, Condensed matter

One-loop approximation for the Heisenberg antiferromagnet

A. Sherman, Michael Schreiber

Published May 14, 2001• 6 citations
arXivHTMLPDF

Abstract

We use the diagram technique for spin operators to calculate Green's functions and observables of the spin-$\frac{1}{2}$ quantum Heisenberg antiferromagnet on a square lattice. The first corrections to the self-energy and interaction are taken into account in the chain diagrams. The approximation reproduces main results of Takahashi's modified spin-wave theory [Phys. Rev. B 40, 2494 (1989)] and is applicable in a wider temperature range. The energy per spin calculated in this approximation is in good agreement with the Monte Carlo and small-cluster exact-diagonalization calculations in the range $0<~T\ensuremath{\lesssim}1.2J$ where J is the exchange constant. For the static uniform susceptibility the agreement is good for $T\ensuremath{\lesssim}0.6J$ and becomes somewhat worse for higher temperatures. Nevertheless the approximation is able to reproduce the maximum in the temperature dependence of the susceptibility near $T=0.9J.$

DOI
10.1103/physrevb.63.214421

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