Springer LINK: The European Physical Journal B - Abstract Volume 5 Issue 2 (1998) pp 193-201

The European Physical Journal B

ISSN: 1434-6028 (printed version)
ISSN: 1434-6036 (electronic version)

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Abstract Volume 5 Issue 2 (1998) pp 193-201

Flow equations and extended Bogoliubov transformation for the Heisenberg antiferromagnet near the classical limit

J. Stein (a)

Institut für Theoretische Physik, Ruprecht-Karls-Universität Heidelberg, Philosophenweg 19, 69120 Heidelberg, Germany

Received: 19 March 1998 / Revised: 2 June 1998 / Accepted: 8 June 1998

Abstract: The Heisenberg spin-S quantum antiferromagnet is studied near the large-spin limit, applying a new continuous unitary transformation which extends the usual Bogoliubov transformation to higher order in the 1/S-expansion of the Hamiltonian. This allows to diagonalize the bosonic Hamiltonian resulting from the Holstein-Primakoff representation beyond the conventional spin-wave approximation. The zero-temperature flow equations derived from the extension of the Bogoliubov transformation to order ${\cal O}(1/S^2 )$ for the ground-state energy, the spin-wave velocity, and the staggered magnetization are solved exactly and yield results which are in agreement with those obtained by a perturbative treatment of the magnon interactions.

PACS. 75.10.Jm Quantized spin models[:AND:] 71.27.+a Strongly correlated electron systems; heavy fermions

(a) email: stein@tphys.uni-heidelberg.de

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