相互作用突然开启后的反铁磁海森伯模型

本文以反铁磁海森伯模型为对象,设想了一个相互作用在t=0时刻开启的非平衡体系.在低温近似下,本文利用重整化群流方程方法讨论了该体系可观测量随时间的演化趋势.本文根据此类体系的特点,给出了获得算符时间演化形式的路径,并成功将其应用于本文所讨论的模型中.其中,本文着重介绍了如何在非平衡自旋体系中应用流方程方法,并利用该方法得到了随时间演化的基态磁化强度,同时论证了该方法处理此类系统的有效性.同时,在与平衡体系基态磁化强度的对比中,发现非平衡可观测量随时间震荡而无法收敛,这一点有别于相互作用突然开关键词：非平衡体系反铁磁海森伯模型流方程方法磁化强度

The antiferromagnetic Heisenberg model after a suddenly switched-on interaction

Based on the Heisenberg model, the anti-ferromagnet following the interaction suddenly switched-on at t=0 is considered in this paper. In the limit of low temperature, the time evolution of observables is analytically studied by utilizing the flow equation method. According to the unique feature of the system, the way to obtain the evolution of observables is shown and applied to the system we focused on. Further, special emphasis is laid on the application of the flow equation method to non-equilibrium magnetic systems so that the validity of the method applied to this kind of systems is traced. By means of this method, the evolution of magnetization of the ground state is traced in detail. It is found that the magnetization oscillates with time rather than converges,which is different from that of non-equilibrium Luttinger liquids.