Unveiling the BEC-droplet transition with Rayleigh superradiant scattering

TL;DR

This paper demonstrates how superradiant light scattering can be used to probe and control the transition from Bose-Einstein condensates to droplets in a dipolar gas, revealing detailed dynamics and phase shifts.

Contribution

It introduces superradiant scattering as a novel tool for studying and controlling the BEC-droplet transition in dipolar quantum gases.

Findings

Superradiant scattering efficiency shows non-monotonic behavior during the transition.

The BEC-droplet phases can be distinguished by expansion dynamics and aspect ratio.

Transition points shift with magnetic field orientation.

Abstract

Light scattering plays an essential role in uncovering the properties of quantum states through light-matter interactions. Here, we explore the transition from Bose-Einstein condensate (BEC) to droplets in a dipolar $^{166}$Er gas by employing superradiant light scattering as both a probing and controlling tool. We observe that the efficiency of superradiant scattering exhibits a non-monotonic behavior akin to the rate of sample expansion during the transition, signaling its sensitivity to the initial quantum state, and in turn, revealing the BEC-droplet transition. Through controlled atom depletion via superradiance, we analyze the sample's expansion dynamics and aspect ratio to identify the BEC-droplet phases distinctly, supported by Gaussian variational ansatz calculations. Finally, using these two approaches, we track how the BEC-droplet transition points shift under varying magnetic field orientations. Our work opens new avenues for studying quantum states through superradiance, advancing our understanding of both the BEC-droplet crossover and its coherence properties.