Group Seminar via Zoom: A new apparatus for superradiance with phase-fluctuating dipolar Bose-Einstein condensates

Bojeong Seo, Quantum Gases Laboratory, HKUST
Group Seminar via video conference (Zoom)
Thursday, September 29, 15:00 pm (MEZ)

Abstract:

Lanthanide (Ln) dipolar atoms provide many benefits for quantum simulation, such as large magnetic moment, rich Feshbach resonance, a wide range of excitation spectrum, and long-lived spin-orbit coupling owing to their many valence electrons. Experiments including the extended Bose–Hubbard model, quantum droplets, and supersolid phases have been actively studied with the Ln atoms. However, it is still difficult to produce Bose-Einstein condensates (BEC) of Ln atoms in a small chamber that is compatible with a high-resolution imaging system. For Ln atoms, a large chamber is mostly required to move the location of the magneto-optical trap away from the relatively strong Zeeman slower. In this talk, I present how we overcame the issue and created spin-polarized condensates of 25,000 Er168 atoms at the temperature of 50 nK. We introduced a two-stage slowing scheme to enhance the MOT loading in a small chamber compatible with the objective lens with an 18 mm working distance. Additionally, I present a new observation of superradiance with phase-fluctuating dipolar BECs. Superradiance is collective spontaneous emission generating a pair of recoiled atom clouds. Although superradiance has been extensively studied in past decades, introducing the controllability to the collective light scattering from phase-coherent condensates with isotropic contact interaction remains challenging. Owing to the distinctive features of erbium, we established two independent methods for controlling superradiance. Near the Feshbach resonance, the threshold of superradiance can be tuned with emerging phase fluctuation. Moreover, asymmetry in the superradiant pair was observed by changing the direction of the external magnetic field. This asymmetry occurred due to the anisotropic excitation spectrum induced by the dipolar interaction between atoms. Our observation paves the way for the new application of matter-wave optics including the control of matter-wave emission.