Radial vortex core oscillations in Bose-Einstein condensates

TL;DR

This paper investigates radial vortex core oscillations in Bose-Einstein condensates, revealing their frequencies and energy levels, and comparing them to Kelvin modes to understand their role in quantum turbulence.

Contribution

It introduces a simplified variational model to analyze radial vortex core modes and compares their properties with Kelvin modes in Bose-Einstein condensates.

Findings

Radial modes have frequencies similar to Kelvin modes.

Radial modes possess higher energy than Kelvin modes.

Kelvin modes remain the dominant energy decay channel.

Abstract

Dilute ultracold quantum gases form an ideal and highly tunable system in which superuidity can be studied. Recently quantum turbulence in Bose-Einstein condensates was reported [PRL 103, 045310 (2009)], opening up a new experimental system that can be used to study quantum turbulence. A novel feature of this system is that vortex cores now have a finite size. This means that the vortices are no longer one dimensional features in the condensate, but that the radial behaviour and excitations might also play an important role in the study of quantum turbulence in Bose-Einstein condensates. In this paper we investigate these radial modes using a simplified variational model for the vortex core. This study results in the frequencies of the radial modes, which can be compared with the frequencies of the thoroughly studied Kelvin modes. From this comparison we find that the lowest (l=0) radial mode has a frequency in the same order of magnitude as the Kelvin modes. However the radial modes still have a larger energy than the Kelvin modes, meaning that the Kelvin modes will still constitute the preferred channel for energy decay in quantum turbulence.