The order parameter of a quantum-coherent many-body system can include a phase degree of freedom, which, in the presence of an electromagnetic field, depends on the choice of gauge. Because of the relationship between the phase gradient and the velocity, …

Gauge matters: observing the vortex-nucleation transition in a Bose condensate Read more »

Spin-orbit coupling is an essential ingredient in topological materials, conventional and quantum-gas-based alike. Engineered spin-orbit coupling in ultracold-atom systems—unique in their experimental control and measurement opportunities—provides a major opportunity to investigate and understand topological phenomena. Here we experimentally demonstrate and …

Tunable Spin-Orbit Coupling via Strong Driving in Ultracold-Atom Systems Read more »

Ultracold gases of interacting spin-orbit-coupled fermions are predicted to display exotic phenomena such as topological superfluidity and its associated Majorana fermions. Here, we experimentally demonstrate a route to strongly interacting single-component atomic Fermi gases by combining an s-wave Feshbach resonance (giving …

Raman-Induced Interactions in a Single-Component Fermi Gas Near an s-Wave Feshbach Resonance Read more »

Zitterbewegung, a force-free trembling motion first predicted for relativistic fermions like electrons, was an unexpected consequence of the Dirac equation’s unification of quantum mechanics and special relativity. Though the oscillatory motion’s large frequency and small amplitude have precluded its measurement with electrons, zitterbewegung is …

Direct observation of zitterbewegung in a Bose–Einstein condensate Read more »