Haldane-gapped spin chains: Exact low-temperature expansions of correlation functions

Article

关键词: NONLINEAR SIGMA-MODEL;    QUANTUM-FIELD-THEORY;    FINITE-TEMPERATURE;    TRANSPORT-PROPERTIES;    CONSERVATION-LAWS;    INTEGRABLE MODELS;    IMPURITY PROBLEMS;    EXTERNAL-FIELD;    ANTIFERROMAGNETS;    DYNAMICS;   

DOI  :  10.1103/PhysRevB.68.104435

来源: SCIE

【 摘 要 】

We study both the static and dynamic properties of gapped, one-dimensional, Heisenberg, antiferromagnetic, spin chains at finite temperature through an analysis of the O(3) nonlinear sigma model. Exploiting the integrability of this theory, we are able to compute an exact low-temperature expansion of the finite temperature correlators. We do so using a truncated form-factor expansion and so provide evidence that this technique can be successfully extended to finite temperature. As a direct test, we compute the static zero-field susceptibility and obtain an exact match to the susceptibility derived from the low-temperature expansion of the exact free energy. We also study transport properties, computing both the spin conductance and the NMR-relaxation rate, 1/T-1. We find these quantities to show ballistic behavior. In particular, the computed spin conductance exhibits a nonzero Drude weight at finite temperature and zero applied field. The physics thus described differs from the spin diffusion reported by Takigawa [Phys. Rev. Lett. 76, 2173 (1996)] from experiments on the Haldane gap material, AgVP2S6.

【 授权许可】

Free