论文标题
具有对称特征性的量子系统中动态相变的理论
Theory of dynamical phase transitions in quantum systems with symmetry-breaking eigenstates
论文作者
论文摘要
我们基于最小的对称假设集，为两种动态量子相变的理论，称为DPT-I和DPT-II。在具有无限范围相互作用的集体系统的特殊情况下，这两者都是由激发态量子相变触发的。对于低于临界能量的淬灭，识别相应阶段的额外保守电荷的存在允许表征dpts-i的动态顺序参数的非零值，并排除了在回报概率中产生非分析性的主要机制，DPTS-II的商标，DPTS-II。我们提出了一个统计集合，描述了DPTS-I中的订单参数的长期平均值，并为DPTS-II的主要机制与存在此额外保守电荷的存在提供了理论上的证据。我们的结果在完全连接的横向场模型中进行了数值说明，该模型表现出两种动态相变。最后，我们讨论了我们的理论对具有有限范围相互作用的系统的适用性，其中不存在激发状态量子相变的现象学。我们通过数值计算以实验相关的初始状态来说明我们的发现。
We present a theory for the two kinds of dynamical quantum phase transitions, termed DPT-I and DPT-II, based on a minimal set of symmetry assumptions. In the special case of collective systems with infinite-range interactions, both are triggered by excited-state quantum phase transitions. For quenches below the critical energy, the existence of an additional conserved charge, identifying the corresponding phase, allows for a nonzero value of the dynamical order parameter characterizing DPTs-I, and precludes the main mechanism giving rise to nonanalyticities in the return probability, trademark of DPTs-II. We propose a statistical ensemble describing the long-time averages of order parameters in DPTs-I, and provide a theoretical proof for the incompatibility of the main mechanism for DPTs-II with the presence of this additional conserved charge. Our results are numerically illustrated in the fully-connected transverse-field Ising model, which exhibits both kinds of dynamical phase transitions. Finally, we discuss the applicability of our theory to systems with finite-range interactions, where the phenomenology of excited-state quantum phase transitions is absent. We illustrate our findings by means of numerical calculations with experimentally relevant initial states.
