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Doctoral Defense: Engineered potentials in ultracold Bose-Einstein condensates

May 5, 2015 - 10:00am
Daniel Campbell
Interacting Bose-Einstein condensates (BECs) are subject to 2-body collisions (interactions) which are well described by a term in the Hamiltonian whose magnitude depends upon the density of particles in the BEC.  These interactions endow BECs with fluid-like properties, e.g. they match the shape of their potential and vortices can appear (sim. to superfluids).  We investigated multi-component BECs which have repulsive overall interactions and very weakly attractive state-dependent (spin) interactions.  We observe the formation of spin-domains seeded by state-dependent noise and the subsequent expansion of these domains once they reach full contrast: at each time we compare the structure of our system to its coherence length.  In a subsequent experiment we prepared our spin-1 BECs in the ground eigenstate of an optical coupling that linked linear momentum and spin (spin-orbit).   We can then define a continuum over which the magnetization of each particle is defined and over which the particle has one or more energetic minima which contribute to the free energy (when uncoupled by spin-orbit coupling the magnetization is the discrete spin of the particle). A combination of collisional interactions, trap dynamics, and evaporation then populate the absolute minimum in the free energy.  Our spin-orbit coupled BECs can undergo a phase transition from unmagnetized to magnetized and are thus a member of a growing class of itinerant ferromagnetic systems: systems where the magnetic particles are free to move about.
Advisor: Dr. Ian Spielman
Dr. Steven Rolston (Committee Chair)

Dr. Mohammad Hafezi

Dr. Amy Mullin

Dr. Trey Porto

2115 Computer and Space Sciences
College Park, MD 20742