# SRS-10/17 Superfluidity under a quench of interaction strength in a persistent current

**Suitable for: **Students interested in theoretical and computational quantum physics.

**Project: **One of the key insights of Landau was to derive a phenomenological formula for the critical velocity in a superfluid. In a Bose gas this is related to the speed of sound, which is directly related to the strength of repulsive interaction between particles. By making use of something known as a "Feshbach resonance" in the scattering properties of two atoms, it is experimentally possible to tune the strength of interactions in a Bose gas. This project will look at a ring system in which there exists a persistent current that if left undisturbed will never decay. However, if the interaction strength is sufficiently reduced, the speed of sound will decrease below the speed of the current and the superflow will break down. This project will characterize the non-equilibrium dynamics as the flow breaks down and thermalizes. It should be able to be related to the well-known "Kibble-Zurek" mechanism for phase transitions.

**Expected outcomes: **A complete set of results with appropriate interpretation could be turned into a publication.

**Duration: **8 weeks; start and finish times flexible.

**Contact: **Professor Matt Davis, mdavis@physics.uq.edu.au or phone +61 7 334 69824; room 309, Physics Annexe (6), UQ St Lucia campus.