Sara Sloman - Thesis Dissertation Defense

In partial fulfillment of the requirements for the degree of 

Doctor of Philosophy in Physics 

School of Physics Thesis Dissertation Defense

Sara Sloman

Dr. Chandra Raman, School of Physics, Georgia Institute of Technology (Advisor)

Understanding and Controlling Nonlinear Dynamics in Magneto-Optical Traps

Virtual:  https://teams.microsoft.com/meet/233914907052583?p=aGoTcFfvh6PPGVoUl1

Thesis Committee: 

Dr. Colin Parker, School of Physics, Georgia Institute of Technology

Dr. Zeb Rocklin, School of Physics, Georgia Institute of Technology

Dr. Carlos Sa De Melo, School of Physics, Georgia Institute of Technology

Dr. Bryan Gard, Georgia Tech Research Institute

Abstract:

Magneto-optical traps (MOTs) are overdamped systems, yet they can be prone to nonlinear dynamics and instabilities under realistic lab conditions. With the increasing importance of cold trapped atoms in atomic physics, it has become vital that we develop an understanding of these behaviors, which limit size and overall quality of the MOT. This dissertation investigates the nonlinear dynamics in a sodium-23 MOT through experimental methods. By varying the location of the trap center, stable and unstable states are reached, revealing a controllable method for tuning between these states. High-speed imaging is used classify these states, and bistable states are resolved among these dynamics at the threshold of instability. To further explore the nonlinear nature of MOTs, an analogy is drawn between the trapped atoms and low Reynolds number fluids, where inertia is negligible. A key feature of low Reynolds number systems is kinematic reversibility, the total reversal of the trajectory of a particle with the reciprocal application of an external force. This dissertation presents the first demonstration of kinematic reversibility in a cold atom fluid, which is achieved using controlled magnetic field ramps. The conditions under which reversibility breaks down are investigated and hypothesized to be due to a fluid-jamming behavior. By controllably tuning the trapping geometry due to beam misalignments, we determine a way to induce the breakdown of reversibility, providing further insight into the mechanisms behind this.