近日，菲律宾大学的Roy D. Jara, Jr&Dennis F. Salinel及其研究团队取得一项新进展。经过不懈努力，他们提出全连接自旋腔系统中离散时间晶体的参量共振理论。相关研究成果已于2024年4月17日在国际知名学术期刊《物理评论A》上发表。

该研究团队从参数共振的视角出发，将各类系统映射至类振子模型，从而确定了在全连接自旋腔系统中形成离散时间晶体（DTC）的必备条件。研究人员进一步通过映射周期性驱动的开放迪克模型，至有效的线性和非线性振荡器模型，深入剖析了非线性和耗散在其中的作用。同时，他们还利用可调各向异性的Lipkin-Meshkov-Glick模型，全面分析了全局对称性破缺的影响。

另一方面，耗散作用使得倍周期不稳定的振荡幅值保持稳定，这正是离散时间晶体的一个核心特征。在没有外部驱动的情况下，研究人员发现全局对称性破缺的存在，对倍周期响应的参数共振激活起到了至关重要的作用。他们借助两种系统各自的振荡器模型，对导致离散时间晶体形成的谐振频率和振幅进行了分析预测。

附：英文原文

Title: Theory of parametric resonance for discrete time crystals in fully connected spin-cavity systems

Author: Roy D. Jara, Jr, Dennis F. Salinel, Jayson G. Cosme

Issue&Volume: 2024/04/17

Abstract: We pinpoint the conditions necessary for discrete time crystal (DTC) formation in fully connected spin-cavity systems from the perspective of parametric resonance by mapping these systems onto oscillatorlike models. We elucidate the role of nonlinearity and dissipation by mapping the periodically driven open Dicke model onto effective linear and nonlinear oscillator models, while we analyze the effect of global symmetry breaking using the Lipkin-Meshkov-Glick model with tunable anisotropy. We show that the system's nonlinearity restrains the dynamics from becoming unbounded when driven resonantly. On the other hand, dissipation keeps the oscillation amplitude of the period-doubling instability fixed, which is a key feature of DTCs. The presence of global symmetry breaking in the absence of driving is found to be crucial in the parametric resonant activation of period-doubling response. We provide analytic predictions for the resonant frequencies and amplitudes leading to DTC formation for both systems using their respective oscillator models.

DOI: 10.1103/PhysRevA.109.042212

Source: https://journals.aps.org/pra/abstract/10.1103/PhysRevA.109.042212