标题： 耦合BEC-腔系统的能带结构：耗散和几何的影响 显示英文标题

标题： Bandstructure of a coupled BEC-cavity system: effects of dissipation and geometry

摘要： 我们提出了一个理论模型，用于描述横向驱动的玻色-爱因斯坦凝聚体与光学腔耦合的情况。我们将重点放在不同相干耦合之间的相互作用上，这些耦合可以触发一种结构相变，即超辐射相变。我们的方法基于能带结构理论和平均场描述，能够全面分析系统激发模式的本质，预示相变的发生。通过纳入这些系统固有的耗散耦合，我们发现了非厄米现象，例如交叉前驱模式的合并以及例外点（EPs）的出现。我们模型的一般表述使我们能够解释横向泵浦与腔体偏离角度不为$90^\circ$时的作用。这为我们提供了关于此类系统各种实现方式的统一视角。 显示英文摘要

摘要： We present a theoretical model for a transversally driven Bose-Einstein condensate coupled to an optical cavity. We focus on the interplay between different coherent couplings, which can trigger a structural phase transition, known as the superradiant phase transition. Our approach, based on band structure theory and a mean-field description, enables a comprehensive analysis of the nature of the system's excited modes, precursing the phase transitions. By incorporating dissipative couplings, intrinsic to these systems, we find non-Hermitian phenomena such as the coalescence of crossing precursor modes and the emergence of exceptional points (EPs). The general formulation of our model allows us to explain the role of an angle between transverse pump and the cavity deviating from $90^\circ$. This offers us a unified perspective on the plethora of different implementations of such systems.