Collapse of a quantum vortex in an attractive two-dimensional Bose gas

TL;DR

This paper investigates the collapse and instability dynamics of quantum vortices in a two-dimensional Bose gas with attractive interactions, revealing self-similar behavior and vortex soliton formation through experiments and simulations.

Contribution

It provides new experimental and numerical insights into vortex collapse, self-similar dynamics, and soliton formation in attractive 2D Bose gases, highlighting effects beyond mean-field theory.

Findings

Vortex collapse leads to quasi-stationary density profiles.

Emergence of vortex soliton-like structures and self-similar dynamics.

Discrepancies indicating effects beyond mean-field approximation.

Abstract

We experimentally and numerically study the collapse dynamics of a quantum vortex in a two-dimensional atomic superfluid following a fast interaction ramp from repulsion to attraction. We find the conditions and time scales for a superfluid vortex to radially converge into a quasi-stationary density profile, demonstrating the spontaneous formation of a vortex soliton-like structure in an atomic Bose gas. We record an emergent self-similar dynamics caused by an azimuthal modulational instability, which amplifies initial density perturbations and leads to the eventual splitting of a solitonic ring profile or direct fragmentation of a superfluid into disordered, but roughly circular arrays of Townes soliton-like wavepackets. These dynamics are qualitatively reproduced by simulations based on the Gross-Pitaevskii equation. However, a discrepancy in the magnitude of amplified density fluctuations predicted by our mean-field analysis suggests the presence of effects beyond the mean-field approximation. Our study sets the stage for exploring out-of-equilibrium dynamics of vortex quantum matter quenched to attractive interactions and their universal characteristics.