This article summarizes some of the relevant features exhibited by binary mixtures of Bose–Einstein condensates in the presence of coherent coupling at zero temperature. The coupling, which is experimentally produced by proper photon transitions, can involve either negligible momentum transfer from the electromagnetic radiation (Rabi coupling) or large momentum transfer (Raman coupling) associated with spin–orbit effects. The nature of the quantum phases exhibited by coherently coupled mixtures is discussed in detail, including their paramagnetic, ferromagnetic, and, in the case of spin–orbit coupling, supersolid phases. The behavior of the corresponding elementary excitations is discussed, with explicit emphasis on the novel features caused by the spin-like degree of freedom. Focus is further given to the topological excitations (solitons, vortices) as well as to the superfluid properties. This review also points out relevant open questions that deserve more systematic theoretical and experimental investigations.

中文翻译：

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超冷原子气体的相干耦合混合物

本文总结了零温度下相干耦合下玻色-爱因斯坦凝聚二元混合物所表现出的一些相关特征。这种耦合是通过适当的光子跃迁在实验上产生的，可以涉及来自电磁辐射的可忽略不计的动量转移（拉比耦合）或与自旋轨道效应相关的大动量转移（拉曼耦合）。详细讨论了相干耦合混合物所表现出的量子相的性质，包括它们的顺磁相、铁磁相，以及在自旋轨道耦合的情况下的超固相。讨论了相应的基本激励的行为，并明确强调了由类自旋自由度引起的新特征。进一步关注拓扑激发（孤子、涡旋）以及超流体特性。这篇综述还指出了值得进行更系统的理论和实验研究的相关开放问题。