论文标题
超级相变的通用类别和精确的相边界
Universality class and exact phase boundary in the superradiant phase transition
论文作者
论文摘要
DICKE模型和RABI模型可以在相同边界处从正常相向超级阶段的相变，可以使用一些近似方法准确地确定。这种巧合的基本机制尚不清楚，这两个模型的普遍性类别难以捉摸。在这里，我们使用基于忠实的Schwinger fermion表示的路径综合方法准确地证明了这种相变，并为这些模型提供了统一的相边界条件。我们证明，在相边界上，骨器场的波动消失了，因此可以将其视为经典场，基于该场开发了一种简化的方法来确定相位边界。这就解释了为什么通过将操作员视为经典变量可以产生确切边界的近似理论。我们使用这种方法来研究几种类似的自旋和玻色子模型，显示出比以前使用的方法更广泛的适用性。我们的结果表明，这些相转换属于相同的普遍性，经典的兰道理论可以在最近的实验中使用平台来确认。
The Dicke model and Rabi model can undergo phase transitions from the normal phase to the superradiant phase at the same boundary, which can be accurately determined using some approximated approaches. The underlying mechanism for this coincidence is still unclear and the universality class of these two models is elusive. Here we prove this phase transition exactly using the path-integral approach based on the faithful Schwinger fermion representation, and give a unified phase boundary condition for these models. We demonstrate that at the phase boundary, the fluctuation of the bosonic field is vanished, thus it can be treated as a classical field, based on which a much simplified method to determine the phase boundary is developed. This explains why the approximated theories by treating the operators as classical variables can yield the exact boundary. We use this method to study several similar spin and boson models, showing its much wider applicability than the previously used approaches. Our results demonstrate that these phase transitions belong to the same universality by the classical Landau theory of phase transitions, which can be confirmed using the platforms in the recent experiments.
