近日，中国科学技术大学Zheng Wei课题组成功实现了量子系统时间晶体跃迁中的模式软化。相关研究成果已于2023年3月14日在国际学术期刊《物理评论A》上发表。

该研究将空间晶体转变中的roton软化机制的概念推广到开放量子系统中的时间晶体。研究人员以耗散的Dicke模型为典型例子进行研究，该模型同时具有连续时间晶体和离散时间晶体相。研究发现，在接近时间晶体跃迁时，响应函数在有限频率上发散，这决定了即将出现的时间晶体的周期。

这种发散可以理解为相应集体激发的弛豫速率的软化，可以从复平面上响应函数的极点清楚地看到。利用这种模式软化分析，研究人员预测了时间准晶相，其中自组织周期和驱动周期是不可调和的。

附：英文原文

Title: Mode softening in time-crystalline transitions of open quantum systems

Author: Xiaotian Nie, Wei Zheng

Issue&Volume: 2023/03/14

Abstract: In this work, we generalize the concept of the roton-softening mechanism of the spatial crystalline transition to time crystals in open quantum systems. We study a dissipative Dicke model as a prototypical example, which exhibits both continuous time crystal and discrete time crystal phases. We find that, on approaching the time crystalline transition, the response function diverges at a finite frequency, which determines the period of the upcoming time crystal. This divergence can be understood as softening of the relaxation rate of the corresponding collective excitation, which can be clearly seen by the poles of the response function on the complex plane. Using this mode-softening analysis, we predict a time quasicrystal phase in our model, in which the self-organized period and the driving period are incommensurate.

DOI: 10.1103/PhysRevA.107.033311

Source: https://journals.aps.org/pra/abstract/10.1103/PhysRevA.107.033311