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arXiv 1909.04337quant-phcond-mat.stat-mech
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多体量子混沌中的离散时间晶体

Discrete time crystals in many-body quantum chaos

Pekik Nurwantoro, Raditya Weda Bomantara, Jiangbin Gong

摘要:

离散时间晶体(DTC)是物质的新相,其特征在于存在在$T$ -周期性哈密顿量下以$nT$周期性演化的可观测量,其中$n>1$是对小参数变化不敏感的整数。特别是,近年来,在周期性淬熄和反冲自旋系统中,已经广泛地研究了具有$n=2$的DTC。在本文中,我们从多体量子混沌的角度来研究DTC的出现,使用一个相当简单的模型描述一个谐波驱动的自旋链。我们主张首先采用半经典近似到达一个平均场哈密顿量,然后确定DTC存在的参数制度,从经典混沌研究借用的标准工具。具体而言,我们寻求破缺的解决方案,通过检查稳定的岛屿上的庞加莱表面的平均场哈密顿。然后,我们转向实际的多体量子系统,评估频闪动力学的总磁化在全量子极限,并验证DTC的存在。我们的有效和直接的方法表明,在一般DTC是一个自然的方面,多体量子混沌与混合经典相空间结构。我们的方法也可以应用到一般的时间周期性系统,这是因此有希望找到DTC与$n>2$和开放的可能性,探索DTC的属性超越其时间平移的突破功能。

英文摘要:

Discrete time crystals (DTCs) are new phases of matter characterized by the presence of an observable evolving with $nT$ periodicity under a $T$-periodic Hamiltonian, where $n>1$ is an integer insensitive to small parameter variations. In particular, DTCs with $n=2$ have been extensively studied in periodically quenched and kicked spin systems in recent years. In this paper, we study the emergence of DTCs from the many-body quantum chaos perspective, using a rather simple model depicting a harmonically driven spin chain. We advocate to first employ a semiclassical approximation to arrive at a mean-field Hamiltonian and then identify the parameter regime at which DTCs exist, with standard tools borrowed from studies of classical chaos. Specifically, we seek symmetric-breaking solutions by examining the stable islands on the Poincare surface of section of the mean-field Hamiltonian. We then turn to the actual many-body quantum system, evaluate the stroboscopic dynamics of the total magnetization in the full quantum limit, and verify the existence of DTCs. Our effective and straightforward approach indicates that in general DTCs are one natural aspect of many-body quantum chaos with mixed classical phase space structure. Our approach can also be applied to general time-periodic systems, which is thus promising for finding DTCs with $n>2$ and opening possibilities for exploring DTCs properties beyond their time-translational breaking features.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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