Zheng-Xin Liu, Yi Zhou, Tai-Kai Ng
In a previous paper [Phys. Rev. B 85,195144 (2012)], we studied the ground state properties of the bilinear-biquadratic S=1 Heisenberg chain using Gutzwiller projected BCS wave functions as trial ground states wavefunctions, and obtained results in excellent agreement with best available results in the Haldane phase and the dimer phase. We extend the approach to study the low-lying spin excitations in this paper and find that the approach works equally well in the two gapped phases of the same model. We especially study the Takhtajan-Babujian (TB) critical point and show that the excitation spectrum, critical exponent ($\eta=0.74$) and central charge ($c=1.45$) calculated numerically from our theory agree well with Bethe ansatz solution and conformal field theory predictions.
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http://arxiv.org/abs/1307.4958
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