Nonequilibrium vortex matter in a strongly interacting quantum fluid
Abstract
Strongly interacting many-body quantum systems exhibit rich behaviors with significance ranging from superconductivity to quantum computation, astrophysics, and even string theory. The first example of such a system, the superfluid, was discovered in cryogenically cooled liquid helium-4 more than 80 years ago. It was found to persist even in very thin two-dimensional films that have fundamentally different nonequilibrium dynamics to three-dimensional materials. It is now recognized these dynamics are dominated by quantized vortices, which are central to Berezinskii, Kosterlitz, and Thouless (BKT) superfluidity, quantum turbulence and anomalous hydrodynamics. Recently, laser control and imaging of vortices in ultracold gases and semiconductor exciton-polariton systems have provided powerful capabilities to study the dynamics of two-dimensional superfluids. However, these experiments are generally limited to the regime of weak interactions, where the GrossÐPitaevskii equation provides a microscopic model of the dynamics of the superfluid. The regime of strong interactions can be reached by tuning the atomic scattering length in ultracold gases, although three-body losses can limit the system lifetime. Superfluid helium, by contrast, exists naturally in this state and can, moreover, be observed non-destructively. As such, superfluid helium is attractive for microscopic studies of quantum fluid dynamics, such as nonequilibrium passage through phase transitions, quantum turbulence and relaxation towards equilibrium. Inspired by the remarkable progress made in the use light to control atomic superfluids, at the University of Queensland we have developed a new technological platform to laser control two-dimensional superfluid helium on a silicon chip. By confining a nanometer thick superfluid helium film on the surface of an optical microcavity, we have shown that it is possible to laser-cool superfluid sound waves, to create a superfluid sound-laser, and to track in real-time the dynamics of quantized vortex clusters. Quite remarkably, we found that the vortex dynamics in thin superfluid helium films is more coherent than is the case even for the very best of atomic condensates. This opens a new path to advance our understanding of the coherent dynamics of vortices Ð how they move and how they interact. This project will build upon our existing technological platform, both using nanophononic crystal structures to increase vortex interactions by orders of magnitude, and using precision microscopy to image clusters of thousands of vortices Ð far beyond the capabilities of any existing technology. This will allow us to answer longstanding questions on how vortices interact, observe recently predicted vortex edge states analogous to fractional quantum Hall states, build the first optical vortex traps, and observe the forces of quantum vacuum on vortices for the first time. Broadly, this will both extend our understanding of nonequilibrium quantum systems, and inform future developments of quantum-vortex technologies for new quantum materials, sensors, and devices.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Apr 19, 2023
- Source ID
- W911NF2310117
Entities
People
- Warwick Bowen
Organizations
- Army Contracting Command
- United States Army
- University of Queensland