Chirality mechanism of spin-glass ordering

自旋玻璃作为一个典型的“复杂”系统被广泛研究，在这个系统中，挫折感和随机性的影响共存。本项目的目的是检验最近提出的实验自旋玻璃有序的手性机制的有效性，以解释实验中的一些谜题。通过对零场下各向同性和弱各向异性三维海森堡自旋玻璃模型的大规模模拟，我们证实了在没有标准自旋玻璃有序的情况下，在有限温度下发生了手性玻璃相变。在真实的自旋玻璃中，微弱但有限的随机磁各向异性不可避免地存在，并有望在自旋玻璃有序化中发挥重要作用。我们还对弱各向异性系统进行了大规模的模拟，得到了支持手性机制预言的自旋-手性重新耦合发生的结果。我们还对磁场中的三维海森堡自旋玻璃进行了大规模的模拟，发现在零场中发生了与零场中相同的手征-玻璃相变，相关联的跃迁线形状在零场极限下是规则的。同样，结果与手性机制的预测是一致的。

Spin glass has been studied quite extensively as a typical example of 'complex' systems where the effects of frustration and randomness coexist. The present project has been performed with the aim of testing the validity of the chirality mechanism of the experimental spin-glass ordering proposed recently to explain some of the puzzles of the experiments. Via large-scale simulations on isotropic as well as weakly anisotropic three-dimensional Heisenberg spin-glass models in zero field, we have confirmed the occurrence of the chiral-glass transition at a finite temperature without the standard spin-glass order. In real spin glasses, weak but finite random magnetic anisotropy inevitably exits and is expected to play an important role in the spin-glass ordering. We have also performed large-scale simulations on the weakly anisotropic systems and have obtained the results supporting the occurrence of the spin-chirality recoupling predicted by the chirality mechanism. We have also performed large-scale simulations for the three-dimensional Heisenberg spin glass in magnetic fields, and found that the chiral-glass transition of the same kind as in zero field occurs, the shape of the associated transition line being regular in the zero-field limit. Again, the results are consistent with the prediction of the chirality mechanism.