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An Experimental Realization of a Griffiths Phase in 87Rb in Three Dimensions

December 6, 2017 - 12:00pm
Matthew Reed
Dissertation Committee Chair: 

Prof. Steven Rolston

Dr. Gretchen Campbell
Dr. Jay Deep Sau
Dr. Ian Spielman
Dr. Mohammad Hafezi
We describe a novel High Bandwidth Arbitrary Lattice Generator (HiBAL) we've created to skirt limits imposed on monochromatic standing waves of light.  With its current iteration we can phase and amplitude modulate optical lattices over a broad range of wavevectors simultaneously at MHz frequencies.  We characterize its behavior with a multi-Mach-Zehnder interferometer and a 0.5 NA diffraction limited imaging system, both designed and built in-house.  We report lattice phase control to within a few parts in a thousand.
Disorder plays an important role in the phase diagrams of many materials.  Crystal defects can cause exotic phases to coexist with the mundane in real world systems, and some phase diagrams are even dominated by the effects of disorder.  We report the trapping and characterization of a Bose gas in an optical field isotropic in two dimensions and disordered in a third.  We evaluate the phase diagram of our system as a function of temperature and disorder depth, and find favorable comparisons with indications of an intermediate Griffiths phase predicted by previous Monte Carlo and Renormalization Group studies separating 2D and 3D superfluid regimes.  
Finally, I discuss the possibility of realizing the BKT transition in a non-orientable space.  The BKT phase transition an infinite order phase transition in two dimensions from a normal gas to a superfluid mediated by vortices, which are orientable topological phase defects in two dimensions.  I discuss the properties of vortices and their intractions on a Mobius strip, and describe how a relay-imaged bichromatic optical potential could be used to form a Mobius strip out of ultracold gases.
PSC 1136