(1) Laboratoire de Physique Quantique, Université Paul Sabatier, 31062 Toulouse Cedex, France, FR;(2) Department of Physics, University of Cincinnati, Cincinnati, Ohio 45221, USA, US
Abstract:
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.
Received 4 January 2000