Chrial Edge States in a Rotating Quantum Gas

We report on the direct, in-situ observation of chiral edge states in a Bose-Einstein condensate subjected to a synthetic magnetic field created using rapid rotation. We demonstrate the use of an underlying scalar potential to smoothly control the momentum of the injected edge mode, and extract the variation in the resulting mode propagation speed. Finally, we explore the dependence of the edge mode speed and excitation energy on the wall sharpness, demonstrating a crossover from ExB behavior to that of an infinitely sharp wall.