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Phys. Rev. B 72, 224412 (2005) [8 pages]

Renormalized excitonic method in terms of block excitations: Application to spin lattices

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Mohamad Al Hajj, Jean-Paul Malrieu, and Nathalie Guihéry
Laboratoire de Physique Quantique, IRSAMC/UMR5626, Université Paul Sabatier, 118 route de Narbonne, F-31062 Toulouse Cedex 4, France

Received 26 October 2004; revised 26 September 2005; published 9 December 2005

Dividing the lattice into blocks with a singlet ground state and knowing the exact low-energy spectrum of the blocks and of dimers (or trimers) of blocks, it is possible to approach the lowest part of the lattice spectrum through an excitonic type effective model. The potentialities of the method are illustrated on the one-dimensional (1D) frustrated chain and the 1∕5-depleted square and the plaquette 2D lattices. The method correctly locates the phase transitions between gapped and nongapped phases.

© 2005 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevB.72.224412
DOI:
10.1103/PhysRevB.72.224412
PACS:
75.10.Jm, 71.10.Fd