The Dicke model describes the coherent interaction of a laser-driven ensemble of two level atoms with a quantized light field. It is realized within cavity QED experiments, which in addition to the coherent Dicke dynamics feature dissipation due to e.g. atomic spontaneous emission and cavity photon loss. Spontaneous emission supports the uncorrelated decay of individual atomic excitations as well as the enhanced, collective decay of an excitation that is shared by $N$ atoms and whose strength is determined by the cavity geometry. We derive a many-body master equation for the dissipative Dicke model including both spontaneous emission channels and analyze its dynamics on the basis of Heisenberg-Langevin and stochastic Bloch equations. We find that the collective loss channel leads to a region of bistability between the empty and the superradiant state. Transitions between these states are driven by non-thermal, markovian noise. The interplay between dissipative and coherent elements leads to a genuine non-equilibrium dynamics in the bistable regime, which is expressed via a non-conservative force and a multiplicative noise kernel appearing in the stochastic Bloch equations. We present a semiclassical approach, based on stochastic nonlinear optical Bloch equations, which for the infinite-range Dicke Model become exact in the large-$N$-limit. The absence of an effective free energy functional, however, necessitates to include fluctuation corrections with $\mathcal{O}(1/N)$ for finite $N<\infty$ to locate the non-thermal first-order phase transition between the superradiant and the empty cavity.
Dicke superradiance in degenerate quantum matter: interplay of exchange statistics and spatial confinement
Friedrich-Alexander Universität Erlangen-Nürnberg (FAU)（埃尔朗根-纽伦堡弗里德里希·亚历山大大学）；Max Planck Institute for the Science of Light（马克斯·普朗克光科学研究所）；TU Darmstadt（达姆施塔特工业大学）
Superradiance enhances and suppresses fermionic pairing based on universal critical scaling in two order parameters systems
State Key Laboratory for Mesoscopic Physics, School of Physics, Frontiers Science Center for Nano-optoelectronics, Peking University（北京大学物理学院介观物理国家重点实验室前沿纳米光电子学中心）；Peking University（北京大学）；Beijing Academy of Quantum Information Sciences（北京量子信息科学研究院）
Disorder-Induced Enhancement of Fermionic Superradiance
CNR-INO（意大利国家研究委员会光学研究所）；University of Trento（特伦托大学）；INFN-TIFPA（意大利国家核物理研究所-特伦托基础物理与应用研究所）；Indian Institute of Science Education and Research Thiruvananthapuram（印度科学教育研究所特里凡得琅分校）
