Hidden continuous symmetry and Nambu-Goldstone mode in a two-mode Dicke model
Hidden continuous symmetry and Nambu-Goldstone mode in a two-mode Dicke model
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二模态 Dicke 模型中的隐藏连续对称性和 Nambu-Goldstone 模态
DOI：
10.1103/physreva.89.023812
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发表时间：
2014-02-10
影响因子：
2.9
通讯作者：
Jia, Suotang
中科院分区：
文献类型：
--
作者：
Fan, Jingtao;Yang, Zhiwei;Jia, Suotang
本文研究了双模迪凯模型的基态和激发态性质。该模型是由多个四能级原子系综同时与两个量子化腔场和两对拉曼激光相互作用而实现的。我们揭示了丰富的相图，包括一个一阶量子相变从电超辐射相的磁超辐射相。特别地，当两个集体原子-光子耦合强度相等时，我们发现双模迪凯模型具有隐藏的连续U（1）对称性。如果这些相同的耦合强度足够强，一个量子相称为电磁超辐射相预测。在这样一个阶段，预测的连续U（1）对称性打破和无隙激发光谱（Nambu-Goldstone模式），这可以通过结合布拉格光谱和腔增强布拉格散射实验测量，从而实现。我们的结果为在量子光学中探索连续对称性模型的物理性质而不使用行波近似铺平了道路。
In this paper we investigate the ground-and excited-state properties of a two-mode Dicke model, which is realized in an ensemble of many four-level atoms interacting simultaneously with two quantized cavity fields and two pairs of Raman lasers. We reveal rich phase diagrams, including a first-order quantum phase transition from an electric superradiant phase to a magnetic superradiant phase. In particular, when the two collective atom-photon coupling strengths are equal, we find a hidden continuous U(1) symmetry for the two-mode Dicke model. If these identical coupling strengths are sufficiently strong, a quantum phase called the electromagnetic superradiant phase is predicted. In such a phase, the predicted continuous U(1) symmetry breaks down and the gapless excitation spectrum (the Nambu-Goldstone mode), which could be measured experimentally by combining Bragg spectroscopy and cavity-enhanced Bragg scattering, is thus achieved. Our results pave the way to explore the physics for a model with continuous symmetry in quantum optics without using the rotating-wave approximation.