The gas phase of vortex matter

Speaker: Dr Tyler Neely
Affiliation: University of Queensland

Abstract

The point vortex approximation for two-dimensional fluid flows describes “vortex matter”, where the constituent particles are the locally swirling elements of the fluid – point vortices. These systems exhibit complex dynamics, owing to long-range interactions and bounded phase spaces, leading to exotic high-energy equilibrium states that can be described by absolute negative Boltzmann temperatures.

Similar to normal matter, chiral vortex matter, consisting of point vortices all with the same sign of circulation, can exhibit solid, liquid, and gas “phases”. While the solid and liquid phases describe a range of phenomena in quantum fluids, such as high-temperature superconductivity, the fractional quantum Hall effect, and rotational glitches in neutron stars, the gas phase has remained experimentally elusive, as it is strongly affected by energy loss.

I will describe our ongoing experiments on the gas phase of chiral vortex matter. By using a uniform disc-shaped Bose-Einstein condensate, we experimentally realise a system of point vortices isolated from the external environment, and we have precise experimental control of the initial energy and angular momentum of the vortices. By initialising the vortices in highly non-equilibrium configurations, we demonstrate thermalisation on experimental timescales. The vortex distributions realised are in excellent agreement with the predictions of the microcanonical ensemble.