RUI: Topological Excitations in Spinor Bose-Einstein Condensates

Amherst College, Amherst MA

Investigators

Abstract

Humans have long had a fascination with symmetry, a concept familiar to anyone who has glanced in a mirror or contemplated their left and right hands. Indeed, symmetry is a fundamental organizing principle that appears in every scientific discipline. In physics, symmetries often manifest themselves in terms of topology, or the study of how shapes and structures may - or may not - be deformed continuously into one another. Topology has recently emerged as an important and increasingly relevant topic in modern physics, as recognized by the 2016 Nobel Prize. Shared topological features in different physical systems permit complementary studies, even when those systems are extremely different. For example, similar physics can be studied both in giant particle accelerators at the highest energies and in tabletop apparatus at the coldest temperatures. The ultracold environment central to this research is a dilute gas cooled to tens of billionths of a degree above absolute zero, at which point it develops properties that make it into a kind of well-controlled "universe" into which may be summoned analogues of particles that might - or, perhaps more interestingly, might not - appear in the "real" universe. This project will study the creation and time-evolution of these particle-like phenomena, including point-like monopoles and extended particles known as "skyrmions" and "knots." Such experiments can provide insight into the phenomena and behavior of many different topological systems, and contribute to emerging technologies based on their manipulation and control. The scientific program will also enhance the relationship between cutting-edge experimental research and undergraduate education by providing technological and scientific training opportunities for several highly motivated undergraduates, as well as for a graduate student researcher. In these ways it contributes to the education of the next generation of citizen-scientists. Particle-like topological structures are ubiquitous in physics, appearing in cosmology, particle physics, and condensed-matter physics, among others. They can exhibit a surprising degree of persistence, as they are characterized by a conserved topological charge. Superfluids, such as dilute-gas Bose-Einstein condensates, provide new and exciting opportunities to examine these excitations in highly-controlled environments. The underlying symmetries (and magnetic phases) of a superfluid determine what kinds of topological excitations it can support. This experimental research program examines three-dimensional topological excitations within spin-1 and spin-2 Bose-Einstein condensates, including monopoles, knots, and skyrmions. The spin-1 experiments will explore the time evolution of the excitations following their creation. The spin-2 experiments will begin by creating and exploring the topological excitations permitted by the wider variety of available magnetic phases, and answer similar questions about their time-evolution. The excitations will be created by exposing the condensate to time-dependent magnetic and optical fields, and will be subsequently characterized by close examination of the superfluid using established imaging techniques. The results are expected to contribute directly to our scientific understanding of topological excitations across the many branches of physics in which they appear. The scientific program will also enhance the relationship between cutting-edge experimental research and undergraduate education by providing technological and scientific training opportunities for several highly motivated undergraduates, as well as for a graduate student researcher. 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.