Observation of superradiant light scattering from a phase fluctuating dipolarBose-Einstein condensate

Collective light scattering in a Bose-Einstein condensate (BEC) has been extensively studied by

using its unique coherence property. However, most experiments have explored superradiant light

scattering with closed-shell atoms (e.g. alkali and alkaline-earth-like atoms) in the regime where

only s-wave interactions are present. Here, we experimentally combine tunable s-wave scattering

with dipolar interactions in a BEC of Er atoms. By tuning s-wave interaction strength through

the Feshbach resonance, we tune the superradiance threshold with increasing phase fluctuations.

We also observe an asymmetric superradiant scattering in a dipolar BEC by changing the direction

of the external magnetic field. This collective light scattering opens a new way of probing dipolar

quantum liquids in a BEC.