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9. August 2023 15:00

Geometric Squeezing and Crystallization in Rapidly Rotating Quantum Gases

Prof. Martin Zwierlein
Massachusetts Institute of Technology, Cambridge, MA, USA

Rapidly rotating quantum gases realize the physics of charged particles in high magnetic fields. We developed a novel protocol, geometric squeezing, that enables to create Bose-Einstein condensates in a single Landau gauge wavefunction of the lowest Landau level. Based on the non-commutativity of guiding center X and Y coordinates, geometric squeezing in a saddle potential is a real space analogue to squeezing in phase space of an inverted 1D harmonic oscillator. The condensate’s transverse width shrinks to the Heisenberg-limited ground-state extent of cyclotron motion. Removing the saddle enables studying the evolution of a Landau gauge condensate in "flat land" under the sole influence of interactions. Surprisingly, we find that Landau gauge condensates are unstable towards crystallization into arrays of droplets. This instability of states in the lowest Landau level has its classical analogy in the Kelvin-Helmholtz instability of counterflowing liquids. We explore the crossover of this instability from the lowest Landau level to the Thomas-Fermi regime. I will discuss experiments on observing edge states in confined geometries and prospects to extend this work beyond mean-field quantum Hall states of bosons.