Critical phenomena arise ubiquitously in various contexts of physics, from condensed matter, high-energy physics, cosmology, to biological systems, and consist of slow and long-distance fluctuations near a phase transition or critical point. Usually, these phenomena are associated with the softening of a massive mode. Here, we show that a non-Hermitian-induced mechanism of critical phenomena that does not fall into this class can arise in the steady state of generic driven-dissipative many-body systems with coupled binary order parameters such as exciton-polariton condensates and driven-dissipative Bose-Einstein condensates in a double-well potential. The criticality of this “critical exceptional point” is attributed to the coalescence of the collective eigenmodes that convert all the thermal-and-dissipative-noise-activated fluctuations to the Goldstone mode, leading to anomalously giant phase fluctuations that diverge at spatial dimensions $d\le 4$. Our dynamic renormalization group analysis shows that this gives rise to a strong-coupling fixed point at dimensions as high as $d<8$ associated with a universality class beyond the classification by Hohenberg and Halperin, indicating how anomalously strong the many-body corrections are at this point. We find that this anomalous enhancement of many-body correlation is due to the appearance of a sound mode at the critical exceptional point despite the system's dissipative character.

中文翻译：

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在多体异常点的关键波动

从凝聚态物质，高能物理学，宇宙学到生物系统，物理学中的各种情况中普遍存在临界现象，并且临界现象由相变或临界点附近的缓慢和远距离波动​​组成。通常，这些现象与大规模模式的软化有关。在这里，我们表明，在具有偶合二阶参数（如激子-极化子凝聚和驱动）的泛函驱散型多体系统的稳态下，可能会出现非赫米特诱发的，不属于此类的临界现象的机理。耗散的玻色-爱因斯坦凝聚物在双阱势中。这个“关键的例外点”的重要性归因于合并 将所有由热和耗散噪声激活的涨落转换为Goldstone涨落的集体本征模态，导致异常的巨大相位涨落在空间维度上发散 $d\le 4$。我们的动态重归一化组分析显示，这会在尺寸高达$d<8$与Hohenberg和Halperin所未分类的通用性类别相关，表明此时多体校正的异常强度如何。我们发现，尽管系统具有耗散性，但多体相关性的这种异常增强是由于声音模式出现在关键的异常点。