论文标题
集体系统中的动态和激发量量子过渡
Dynamical and excited-state quantum phase transitions in collective systems
论文作者
论文摘要
我们研究具有无限范围相互作用的量子多体系统中的动力学相变（DPTS），并提出了一种与激发量量子相变（ESQPT）概念相连的两种已知DPT（有时称为DPTS-I和DPTS-II）的理论，传统上是在集体模型中发现的。我们表明，dpts-i在从破碎的对称阶段进行淬灭后，是对称恢复的表现，这两个阶段之间的限制是由ESQPT精确划分的。我们用标准微型典型集合的概括来描述DPTS-I的顺序参数，该集合包含了识别相应阶段的附加保守电荷的信息。我们还表明，dpts-i与ESQPT带来的信息擦除机制有关，并通过我们提出的统计集合来量化此信息损失。最后，我们分析表明，在这些系统中，DPTS-II被禁止在ESQPT的一侧，将破碎的对称性初始状态带到相同的断裂对称阶段，并且根据ESQPT侧的dpts-II的配方，我们提供了DPTS-II的配方。我们分析了DPTS-II的各种指标之间的连接。我们的结果在无限范围的横向场模型中进行了数值说明，并且适用于满足一组条件的大量集体量子系统。
We study dynamical phase transitions (DPTs) in quantum many-body systems with infinite-range interaction, and present a theory connecting the two kinds of known DPTs (sometimes referred to as DPTs-I and DPTs-II) with the concept of excited-state quantum phase transition (ESQPT), traditionally found in collective models. We show that DPTs-I appear as a manifestation of symmetry restoration after a quench from the broken-symmetry phase, the limits between these two phases being demarcated precisely by an ESQPT. We describe the order parameters of DPTs-I with a generalization of the standard microcanonical ensemble incorporating the information of an additional conserved charge identifying the corresponding phase. We also show that DPTs-I are linked to a mechanism of information erasure brought about by the ESQPT, and quantify this information loss with the statistical ensemble that we propose. Finally, we show analytically that DPTs-II are forbidden in these systems for quenches leading a broken-symmetry initial state to the same broken-symmetry phase, on one side of the ESQPT, and we provide a formulation of DPTs-II depending on the side of the ESQPT where the quench ends. We analyze the connections between various indicators of DPTs-II. Our results are numerically illustrated in the infinite-range transverse-field Ising model and are applicable to a large class of collective quantum systems satisfying a set of conditions.
