标题： 等离子体晶格激光器中的自发对称性破缺 显示英文标题

标题： Spontaneous symmetry breaking in plasmon lattice lasers

摘要： 自发对称性破缺（SSB）对于我们理解相变和秩序的自发出现至关重要。光子学提供了多功能的系统来研究SSB。在本工作中，我们报告说，对于具有增益的二维（2D）周期性非局部超表面，在激光跃迁中会发生SSB，打破宇称对称性。我们研究了衍射六边形等离激元纳米粒子晶格，其中动量空间中的K点提供了两个频率完全简并且在空间中分布相同的模式。使用飞秒脉冲激励增益介质，我们同时捕获了激光发射的单次实空间和波矢分辨傅里叶图像。通过结合傅里叶空间和实空间，我们解析了同时发生对称性破缺的两个序参量：空间宇称和U（1）（旋转）对称性破缺，分别表现为随机的相对模式幅度和相位。因此，我们首次量化了二维周期性超表面上的SSB。这些目前受到广泛关注，作为实验可实现的基本固态物理哈密顿量，并为在不同对称性、模式简并和拓扑特性的情况下探索SSB提供了广阔的设计空间。本工作中报告的方法通常适用于二维等离激元和介电超表面，并为研究SSB以及在超光子学中空间相干性的出现开辟了许多机会。 显示英文摘要

摘要： Spontaneous symmetry breaking (SSB) is key for our understanding of phase transitions and the spontaneous emergence of order. Photonics provide versatile systems to study SSB. In this work, we report that for a two-dimensional (2D) periodic nonlocal metasurface with gain, SSB occurs in the lasing transition, breaking parity symmetry. We study diffractive hexagonal plasmon nanoparticle lattices, where the K-points in momentum space provide two modes that are exactly degenerate in frequency and identically distributed in space. Using femtosecond pulses to energize the gain medium, we simultaneously capture single shot realspace and wavevector resolved Fourier images of laser emission. By combining Fourier- and real-space, we resolve the two order parameters for which symmetry breaking simultaneously occurs: spatial parity and U(1) (rotational) symmetry breaking, evident respectively as random relative mode amplitude and phase. Thereby, we quantify for the first time SSB in 2D periodic metasurfaces. These currently receive much interest as experimentally accessible implementations of seminal solid-state physics Hamiltonians and provide a large design space for exploring SSB in scenarios with different symmetries, mode degeneracies and topological properties. The methodology reported in this work is generally applicable to 2D plasmonic and dielectric metasurfaces and opens numerous opportunities for the study of SSB and emergence of spatial coherence in metaphotonics.