Ballistic atom pumps

• Main Author: Byrd, Tommy
• Format: Others
• Language: English
• Published: W&M ScholarWorks 2015
• Online Access: https://scholarworks.wm.edu/etd/1539623999; https://scholarworks.wm.edu/cgi/viewcontent.cgi?article=3672&context=etd

Researchers have long been interested in electron transport through mesojunctions containing time-dependent potential energies, a process often called "quantum pumping." A useful model of such a system is a ballistic atom pump, which consists of two reservoirs of neutral ultracold atoms connected by a channel containing oscillating repulsive potential-energy barriers. Under certain conditions, such pumps can create net transport of atoms from one reservoir to the other, and energy can be pumped out of or into each reservoir even when there is no net particle transport. These pumps are studied from classical and quantum-mechanical perspectives, and semiclassical theory is used to explain some scattering properties which are not easily explained by quantum theory. This system is also a nice model of chaotic transport. Escape-time plots showing the time for classical trajectories to escape the barrier region display a type of fractal self-similarity. A topological theory using a discrete map of the system in the phase plane is developed, and this theory predicts and explains the features seen in escape-time plots.