Phase transition, phase separation and mode softening of a two-component Bose-Einstein condensate in an optical cavity

TL;DR

This paper explores the phase transition, phase separation, and mode softening in a two-component Bose-Einstein condensate within an optical cavity, revealing unique behaviors driven by atomic detunings and superradiant phenomena.

Contribution

It introduces a comprehensive analysis of how atomic detunings influence phase transitions and superradiance in a two-component BEC, highlighting novel phase diagrams and excitation spectra.

Findings

Red-detuned component dominates phase transition.

Spontaneous phase separation with stripe patterns.

Roton mode softening indicates superfluid-lattice transition.

Abstract

We investigate the superradiant phase transition in a two-component Bose-Einstein condensate with distinct atomic detunings, confined in an optical cavity and driven by a transverse pump laser. By combining perturbation theory and numerical simulations, we demonstrate that the phase transition is dominated by the red-detuned component, resulting in a phase diagram completely different from that of a single-component case under blue-detuned condition. The system exhibits spontaneous phase separation between the two components, manifested as alternating stripe patterns in the normal phase and distinct Bragg gratings in the superradiant phase. Furthermore, the Bogoliubov excitation spectrum reveals roton-type mode softening, indicating that the phase transition also corresponds to the superfluid-to-lattice supersolid transition. Our findings provide insights into the interplay between atomic detunings and collective quantum many-body phenomena, offering potential applications in quantum simulation and optical switching technologies.