Scattering of a massive quantum vortex-dipole from an obstacle

Abstract

In binary mixtures of Bose-Einstein condensates, massive-vortex dipoles can arise, and undergo scattering processes against obstacles. These show an intriguing dynamics, governed by the strongly nonlinear character of the quantum vortex motion, where we are able to highlight the effects of the boundaries. We first characterize such scattering dynamics via some point-like models, for the cases of an unbounded plane and a confined geometry. Within this framework, we find two fundamental scattering behaviors of a vortex dipole, the "fly-by" and the "go-around" processes. By plotting the deflection angle of the dipole versus the impact parameter we are able to quantify the transition between different scattering behaviors. We then are able to introduce an analytical distinction of the two scenarios, basing on the point-like model for the plane geometry. Furthermore, another interesting result shows the emergence of an on-average massless dynamics whenever the nonlinear interactions with the obstacle become negligible. Alongside, we investigate the quantum dipole scattering via the numerical simulation of two coupled Gross-Pitaevskii equations, describing the quantum mixture at a mean-field level. In this way, we benchmark the point-like model against the mean-field simulations.