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Phase Transitions in Engineered Ultracold Quantum Systems

November 24, 2015 - 10:00am
Ryan Price
The study of quantum degenerate gases has many applications in topics such as condensed matter dynamics, precision measurements and quantum phase transitions. We built an apparatus to create 87Rb Bose-Einstein condensates (BECs) and generated, via optical and magnetic interactions, novel quantum systems in which we studied the contained phase transitions. 
For our first experiment we quenched multi-spin component BECs from a miscible to dynamically unstable immiscible state. The transition rapidly drives any spin fluctuations with a coherent growth process driving the formation of numerous spin polarized domains. At much longer times these domains coarsen as the system approaches equilibrium. 
For our second experiment we explored the magnetic phases present in a spin-1 spin-orbit coupled BEC and the quantum phase transitions between these phases. We observed ferromagnetic and unpolarized phases which are stabilized by the spin-orbit coupling’s explicit locking between spin and motion. These two phases are separated by a critical curve containing both first-order and second-order transitions joined at a critical point. The narrow first-order transition gives rise to long-lived metastable states. 
For our third experiment we prepared pairs of independent BECs in a double-well potential, with an artificial magnetic field present in the barrier separating the BECs. We then transitioned to a single BEC by lowering the barrier while expanding the region of artificial field to uniformly cover the resulting single BEC.  We compared the distribution of vortices that were nucleated via conventional dynamics to those produced by our procedure, showing our dynamical process populates vortices much more rapidly and in larger number than conventional nucleation.
Dissertation Committee Chair: Prof. Steven Rolston
Dr. Alexey Gorshkov
Dr. Victor Galitski
Dr. Ian Spielman
Dr. Christopher Reynolds
2115 Computer and Space Sciences
College Park, MD 20742

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