Instabilities, where initially small fluctuations seed the formation of large-scale structures, govern the dynamics in various fluid flows. The Rayleigh-Taylor instability (RTI) is an iconic example that leads to the development of mushroom-shaped incursions when immiscible fluids are accelerated into each other. RTI drives structure formation throughout science and engineering including table-top oil and water mixtures; supernova explosions; and inertial confinement fusion. Despite its ubiquity, controlled laboratory RTI experiments are technically challenging. Here we report the experimental observation of RTI in an initially phase-separated binary superfluid consisting of a two-component Bose-Einstein condensate of 23Na atoms. We induce the RTI at the interface between these components using a magnetic gradient force (i.e. the Stern-Gerlach effect) to press the components together and observe the growth of mushroom-like structures. The interface becomes stable when the components are pulled apart, and we spectroscopically measure the dispersion relation of the "ripplon'' interface modes.
Pizza and drinks will be served after the seminar in ATL 2117.
