Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164, USA.
Department of Physics, The University of Texas at Dallas, Richardson, Texas 75080, USA.
Nat Commun. 2014 Jun 4;5:4023. doi: 10.1038/ncomms5023.
Spin-orbit-coupled Bose-Einstein condensates (BECs) provide a powerful tool to investigate interesting gauge field-related phenomena. Here we study the ground state properties of such a system and show that it can be mapped to the well-known Dicke model in quantum optics, which describes the interactions between an ensemble of atoms and an optical field. A central prediction of the Dicke model is a quantum phase transition between a superradiant phase and a normal phase. We detect this transition in a spin-orbit-coupled BEC by measuring various physical quantities across the phase transition. These quantities include the spin polarization, the relative occupation of the nearly degenerate single-particle states, the quantity analogous to the photon field occupation and the period of a collective oscillation (quadrupole mode). The applicability of the Dicke model to spin-orbit-coupled BECs may lead to interesting applications in quantum optics and quantum information science.
自旋轨道耦合玻色-爱因斯坦凝聚体（BEC）为研究有趣的规范场相关现象提供了有力工具。在这里，我们研究了该系统的基态性质，并表明它可以映射到量子光学中著名的 Dicke 模型，该模型描述了原子集合与光场之间的相互作用。Dicke 模型的一个重要预测是超辐射相和正常相之间的量子相变。我们通过在相变过程中测量各种物理量来检测自旋轨道耦合 BEC 中的这种相变。这些量包括自旋极化、近简并单粒子态的相对占据、类似于光子场占据的量以及集体振荡（四极模式）的周期。Dicke 模型在自旋轨道耦合 BEC 中的适用性可能会导致量子光学和量子信息科学中的有趣应用。
