Mechanism for sound dissipation in a two-dimensional degenerate Fermi gas

TL;DR

This study investigates how sound waves propagate and dissipate in a two-dimensional degenerate Fermi gas near superfluid transition temperatures, highlighting the impact of interactions and vortex-antivortex pairs.

Contribution

It introduces a numerical approach incorporating thermal fluctuations to analyze sound attenuation and velocity in 2D Fermi gases across different interaction regimes.

Findings

Sound velocity depends on temperature and interaction strength.

Vortex-antivortex pairs significantly contribute to sound dissipation.

Thermal fluctuations influence transport properties near superfluid transition.

Abstract

We numerically study the transport properties of a two-dimensional Fermi gas in a weakly and strongly interacting regimes, in the range of temperatures close to the transition to a superfluid phase. For that we excite sound waves in a fermionic mixture by using the phase imprinting technique, follow their evolution, and finally determine both their speed and attenuation. Our formalism incorporates thermal fluctuations via the ground canonical ensemble description and with the help of Metropolis algoritm. From numerical simulations we extract temperature dependence of the sound velocity and diffusivity as well as the dependence on the interaction strength. We emphasize the role of virtual vortex-antivortex pairs creation in the process of sound dissipation.