Observation of a spinning top in a Bose-Einstein condensate

Boundaries strongly affect the behavior of quantized vortices in Bose-Einstein condensates, a phenomenonparticularly evident in elongated cigar-shaped traps where vortices tend to orient along a short direction tominimize energy. Remarkably, contributions to the angular momentum of these vortices are tightly confinedto the region surrounding the core, in stark contrast to untrapped condensates where all atoms contribute ¯h.We develop a theoretical model and use this, in combination with numerical simulations, to show that suchlocalized vortices precess in a manner analogous to that of a classical spinning top. We experimentally verifythis spinning-top behavior with our real-time imaging technique that allows for the tracking of position andorientation of vortices as they dynamically evolve. Finally, we perform an in-depth numerical investigation ofour real-time expansion and imaging method, with the aim of guiding future experimental implementation aswell as outlining directions for its improvement.