Mid Term Review

Mutual friction and diffusion of two-dimensional quantum vortices

Mr Zain Mehdi
Dept of Quantum Science & Technology, Research School of Physics, ANU

Turbulence is a universal phenomenon, occurring in fluid flow at all scales of the universe, and is one of the most important research fields in modern physics.

In superfluids, turbulent flow is constrained by the quantization of vorticity and is characterized by the chaotic motion of many quantum vortex filaments. In two-dimensional (2D) superfluids, turbulence is further constrained, as vortices are forced to align with the tightly-confined axis and move like points in the plane. As a result, these systems realize a minimal model of turbulence with a finite number of degrees of freedom, known as two dimensional quantum turbulence (2DQT).

The main theoretical tool to understanding 2DQT is the point-vortex model (PVM), which describes the motion of each point-like vortex in the local flow induced by all other vortices. The PVM is an excellent description of modern 2DQT experiments, provided a damping term is added to model friction between the superfluid and a static thermal cloud. Damping is added phenomenologically, and currently has no established microscopic origin.

In this talk, I will discuss present a microscopic theory for vortex dynamics in a two-dimensional atomic superfluid at finite temperature. This theory is derived from a first-principles treatment of the finite-temperature atomic gas, and accounts for both damping of vortex motion, as well as Brownian motion due to thermal fluctuations. Our theory is in excellent agreement with experimental data provides the precise microscopic mechanism underlying vortex damping phenomenology. This work opens the door for ab initio modelling of 2DQT experiments using stochastic point-vortex theory.

I will also discuss possibilities for adapting the approach used in this work to study other aspects of quantum turbulence.

Zoom details:
https://anu.zoom.us/j/89583788817?pwd=WVpOSVlWR3lRWS9GNzh3NW5oYXI5Zz09
Meeting ID: 895 8378 8817
Password: 121855

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