U(2)振动子模型中的量子相变与临界点对称性

Quantum phase transition in the U(2) vibron model and the critical point symmetry

本文研究了U(2)振动子模型在大N极限以及有限N情况下的量子相变行为,并讨论了临界点对称性概念在一维系统中的适用性.通过对U(2)振动子模型的势能结构,低激发谱等动力学性质的分析,我们发现系统在临界点处是最容易激发的,其低激发动力学特征可以由E(1)临界点对称性近似地描述,但随着激发能增加,近似逐渐破坏.进一步我们又数值分析了临界点处能谱的玻色子数依赖规律,结果表明二级相变临界点处的能谱随玻色子数变化的指数规律是不依赖维数的.

The quantum phase transition in the U（2） vibron model is investigated in large-N limit with the coherent state method and for finite N in a numerical scheme Through analyzing the potential structure and the corresponding low-lying spectrum, it is found that the dynamical characters at the critical point can be approximately described by the E（1） critical point symmetry, but such an approximation becomes poor with the increasing of the excitation energy. In addition, the scaling behavior of the spectrum at the critical point has been also investigated in a numerical way. The results indicate that the scaling law of the spectrum at the critical point of the 2nd order phase transition may be independent of the dimension of system.