Journal of the Physical Society of Japan
A New Phase of theS=1 Bilinear-Biquadratic Chain: -a Trimerized State-
K. Nomura, Satoshi Takada
Abstract
We investigate the S =1 bilinear-biquadratic model. In some region, the trimerized variational state is a good candidate for the ground state. This explains why the Sutherland model ( J 1 >0 and J 2 / J 1 =-1) has soft modes at q =0, ±2π/3. Moreover, the full phase diagram of this model is discussed. It is found that at the pure biquadratic ferromagnetic point, the ground state is extremely degenerate.