On the origin of biquadratic exchange in spin 1 chains

One-dimensional spin 1 systems may have a rich phase diagram including Haldane gap and dimerized phases if the usually very small biquadratic exchange becomes significant. We show that this unlikely condition may be fulfilled in electron systems with quasi-degenerate orbitals. This mechanism may have been experimentally realized in the spin 1 chain LiVGe₂O₆. The implications for the exploration of the physics and quantum chemistry of spin 1 chains are discussed.

Authors and Affiliations

1. Laboratoire de Physique Quantique, Université Paul Sabatier, 31062, Toulouse Cedex, France

   F. Mila

2. Department of Physics, University of Cincinnati, Cincinnati, 45221, Ohio, USA

   Fu-Chun Zhang

Received 4 January 2000

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