Hard-core magnons in the S=12 Heisenberg model on the square lattice

K. P. Schmidt and G. S. Uhrig
Phys. Rev. B 73, 172407 – Published 12 May 2006

Abstract

We propose a versatile approach to treat commonly arising constraints. It is illustrated for interacting magnons of the Heisenberg antiferromagnet on a square lattice. For systems of L×L sites a nonperturbative continuous unitary transformation (CUT) is used to derive an effective Hamiltonian conserving the number of magnons. They are bosonic particles with a hard-core constraint which is captured by a local, repulsive interaction U. The limits U and L are achieved by extrapolation. The residual spin gap Δ1 is smaller than 0.01J reflecting the gapless nature of the magnons. The one-magnon dispersion displays all known characteristics.

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  • Received 12 December 2005

DOI:https://doi.org/10.1103/PhysRevB.73.172407

©2006 American Physical Society

Authors & Affiliations

K. P. Schmidt*

  • Institute of Theoretical Physics, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland

G. S. Uhrig

  • Theoretische Physik, FR 7.1, Geb. E2.6, Universität des Saarlandes, D-66123 Saarbrücken, Germany

  • *Electronic address: kaiphillip.schmidt@epfl.ch; URL: http://marie.epfl.ch/∼kpschmid
  • Present address: Lehrstuhl für theoretische Physik I, Universität Dortmund, 44221 Dortmund, Germany.

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Vol. 73, Iss. 17 — 1 May 2006

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