Enhanced stripe phases in spin-orbit-coupled Bose-Einstein condensates in ring cavities

TL;DR

This paper demonstrates that in spin-orbit-coupled Bose-Einstein condensates within ring cavities, cavity-mediated interactions can stabilize stripe phases over plane-wave phases, revealing new superfluid behaviors and excitation spectra.

Contribution

It introduces the influence of cavity quantum electrodynamics in weak coupling regimes on the ground state phases of spin-orbit-coupled BECs, highlighting the stabilization of stripe phases.

Findings

Stripe phase is energetically favored with increased cavity interactions.

Both phases exhibit superfluidity with linear excitation spectra.

The plane-wave phase shows a roton-like feature in excitations.

Abstract

The coupled dynamics of the atom and photon fields in optical ring cavities with two counter-propagating modes give rise to both spin-orbit interactions as well as long-ranged interactions between atoms of a many-body system. At zero temperature, the interplay between the two-body and cavity-mediated interactions determines the ground state of a Bose-Einstein condensate. In this work, we find that cavity quantum electrodynamics in the weak-coupling regime favors a stripe-phase state over a plane-wave phase as the strength of cavity-mediated interactions increases. Indeed, the stripe phase is energetically stabilized even for condensates with attractive intra- and inter-species interactions for sufficiently large cavity interactions. The elementary excitation spectra in both phases correspond to linear dispersion relation at long wavelengths, indicating that both phases exhibit superfluidity, though the plane-wave phase also displays a characteristic roton-type feature. The results suggest that even in the weak coupling regime cavities can yield interesting new physics in ultracold quantum gases.