RUI: Creating and Studying Topological Excitations in Spinor Bose-Einstein Condensates

Amherst College, Amherst MA

Investigators

Abstract

A primary goal of physics is to understand how different systems fit together within a universal physical framework. One unifying theme involves topological excitations. (A topological excitation is a physical feature of matter that cannot appear smoothly, such as a hole poked in a piece of clay: either the hole is present, or it is not.) Studying these excitations in one system can provide knowledge of other systems that are more difficult or impossible to study experimentally. This project involves experiments on a gas of atoms at temperatures near absolute zero to create and study certain topological excitations. Remarkably, the physics of these excitations in the cold gas is analogous to that of neutron stars in one context, atomic nuclei in another, and fundamental particles in a third. All these systems would otherwise be challenging to study directly. The project also extends new electric and optical technologies to create topological excitations in a controllable manner using shaped laser beams. The goal in this part is to create and study multiple interacting excitations, which will provide further insight into the physical systems that exhibit such phenomena. Finally, a major educational component of the scientific program is the lab experience gained by undergraduate students as they work on the experiments. This contributes to the training of the next generation of physicists and scientists. This project explores the rich physics of topological excitations, such as vortices, monopoles, and skyrmions, within the environment of spin-2 dilute-gas atomic Bose-Einstein condensates (BECs) of Rb-87. Topological excitations are a unifying theme of many diverse branches of physics, where (for example) vortices in a superfluid are analogous to cosmic strings, monopoles in a solid-state system resemble theoretically proposed elementary particles, and skyrmions in a magnetic material appear in the context of atomic nuclei. Of particular interest is the study of spin-2 vortices, which can exist in magnetic phases with discrete polytope internal symmetries and are predicted to exhibit exotic collisions and fractional quantization. The proposal will also further the development of optical techniques for the creation of multiple interacting topological excitations, making use of modern light modulation devices to generate synthetic magnetic fields from vector light shifts, or using their phase and amplitude modulation properties to write excitations into the condensates directly. The results of this research in the atomic system will contribute directly to the scientific understanding of topological excitations across the many branches of physics in which they appear. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.