Abstract

We investigate quantum phase transitions, quantum criticality, and Berry phase for the ground state of an ensemble of non-interacting two-level atoms embedded in a non-linear optical medium, coupled to a single-mode quantized electromagnetic field. The optical medium is pumped externally through a classical electric field, so that there is a degenerate parametric amplification effect, which strongly modifies the field dynamics without affecting the atomic sector. Through a semiclassical description the different phases of this extended Dicke model are described. The quantum phase transition is characterized with the expectation values of some observables of the system as well as the Berry phase and its first derivative, where such quantities serve as order parameters. It is remarkable that the model allows the control of the quantum criticality through a suitable choice of the parameters of the non-linear optical medium, which could make possible the use of a low intensity laser to access the superradiant region experimentally.

Graphical abstract

中文翻译：

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扩展Dicke模型中的量子相变和Berry相

摘要

我们研究嵌入到非线性光学介质中的非相互作用两能级原子团的基态的量子相变，量子临界和Berry相，并耦合到单模量化电磁场。光学介质通过经典电场从外部泵送，因此存在退化的参量放大效应，该效应可以在不影响原子扇区的情况下极大地改变场动力学。通过半经典描述，描述了此扩展Dicke模型的不同阶段。量子相变的特征在于系统某些可观测值的期望值以及贝里相及其一阶导数，其中此类量用作阶跃参数。

图形概要