发表机构
Fudan University; Hefei National Laboratory（复旦大学; 合肥国家实验室）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
通过复制扭曲熵作为探针，在SYK模型中研究费米子非高斯性，揭示动态相图及对称性破缺，为强关联系统非高斯性研究开辟新途径。
AI 中文摘要
理解量子多体系统的非平衡动力学在现代多体物理中扮演核心角色。通过研究量子资源（这些资源对于实现明确的量子性至关重要）在混沌量子动力学下如何产生和传播，可以得出有趣的见解。在费米子系统中，非高斯性构成了超越纠缠的重要资源，表征了通用量子态与自由费米子态的偏差。在本信中，我们提出使用复制扭曲熵（通过可调角度$\alpha$的复制旋转算符的期望值定义）作为纯费米子态中非高斯性的自然探针。在推导其在典型多体态中的行为后，我们建立了一个通用框架，用于在大$N$极限下分析可解的Sachdev-Ye-Kitaev模型中的复制扭曲熵。将该框架应用于热场双态的动态，我们在$\alpha$和演化时间$t$的参数空间中揭示了一个新颖的动态相图，表现出在$\alpha=\pi/4$处的自发$Z_2$对称性破缺，以及在长时间区域内作为$\alpha$函数的普适尖点。我们的结果为研究强关联费米子系统中的非高斯性铺平了道路，并揭示了由非高斯性探测的一类新的动态转变。
英文摘要
Understanding the non-equilibrium dynamics of quantum many-body systems plays a central role in modern many-body physics. Intriguing insights emerge from investigating how quantum resources, which are essential for achieving unambiguous quantumness, are generated and spread under chaotic quantum dynamics. In fermionic systems, non-Gaussianity constitutes an important resource beyond entanglement, characterizing the deviation of generic quantum states from free-fermion states. In this Letter, we propose using the \textit{replica twist entropy}, defined through the expectation value of a replica rotation operator with a tunable angle $α$, as a natural probe of non-Gaussianity in pure fermionic states. After deriving its behavior for typical many-body states, we establish a general framework for analyzing the replica twist entropy in solvable Sachdev-Ye-Kitaev models in the large-$N$ limit. Applying this framework to the dynamics of the thermofield double state, we uncover a novel dynamical phase diagram in the parameter space of $α$ and evolution time $t$, exhibiting spontaneous $Z_2$ symmetry breaking at $α=π/4$ and universal cusps as a function of $α$ in the long-time regime. Our results pave the way for studying non-Gaussianity in strongly correlated fermionic systems and reveal a new class of dynamical transitions probed by non-Gaussianity.
Comments7 pages, 2 figures
