Dicke-type phase transition in a spin-orbit coupled Bose-Einstein condensate

TL;DR

This paper demonstrates a Dicke-type quantum phase transition in a spin-orbit coupled Bose-Einstein condensate, linking condensed matter phenomena with quantum optics models and observing measurable physical changes across the transition.

Contribution

It establishes a mapping between spin-orbit coupled BECs and the Dicke model, revealing a quantum phase transition in such systems for the first time.

Findings

Detection of the superradiant phase transition in BECs

Measurement of spin polarization and occupation changes

Observation of collective oscillation period shift

Abstract

Spin-orbit coupled Bose-Einstein condensates (BECs) provide a powerful tool to investigate interesting gauge-field related phenomena. 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. Here 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.