发表机构
Aalto University School of Science; University of St Andrews（阿尔托大学理学院; 圣安德鲁斯大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过测量等离子体晶格中极化子发射的二阶相干函数，展示了高度相干态（g^(2)(0)-1<10^-4）及超快（>1 THz）动力学，并提出了BEC或超辐射的物理解释。
AI 中文摘要
强耦合系统中支持极化子激射和玻色-爱因斯坦凝聚（BEC）的一阶相干性质已被深入研究，并显示出一致的结果。相比之下，二阶相干性质在不同系统中表现出差异，且二阶相干函数可能偏离原子BEC中典型的数值1，即使在BEC/极化子激射阈值以上也揭示出超泊松涨落。这要求对基于光的凝聚体中的发射统计和动力学有更深入的理解，尤其是在非平衡状态下。在这里，我们展示了从等离子体晶格中极化子发射的相干态，分别对Γ点和非Γ点辐射（基态和高能尾部）测量了二阶相干函数值。我们观察到高度相干性，其值为$g^{(2)}(\ au=0)-1<10^{-4}$。我们还证明了动力学的超快（>1 THz）特性。该过程可以解释为具有超快、亚50飞秒热化过程的BEC，但我们也提出另一种解释，即发射体具有振动自由度的系统中的超辐射。
英文摘要
The first-order coherence properties of strongly coupled systems supporting polariton lasing and Bose-Einstein condensation (BEC) have been thoroughly studied and show consistent results. In contrast, second-order coherence properties have been found to vary for different systems, and the second-order coherence function can deviate from the value of one, typical for atomic BEC, revealing super-Poissonian fluctuations even above the BEC/polariton lasing threshold. This calls for a deeper understanding of the emission statistics and dynamics in light-based condensates, especially in the non-equilibrium regime. Here we demonstrate a coherent state of polariton emission from a plasmonic lattice measured as the second-order coherence function value separately for $\mathrmΓ$- and non-$\mathrmΓ$-point radiation (ground state and high-energy tail). We observe a high degree of coherence with the value $g^{(2)}(τ=0)-1<10^{-4}$. We also demonstrate the ultrafast ($>$1 THz) nature of the dynamics. The process can be interpreted as a BEC with ultrafast, sub-50-fs thermalization, but we also suggest an alternative explanation as superradiance in a system where the emitters have vibrational degrees of freedom.
