Jones-Roberts solitary waves and the onset of rotation in a spherical surface condensate

TL;DR

This paper investigates nonlinear excitations in a spherical Bose-Einstein condensate, revealing how solitary waves evolve with increasing rotation speed and identifying a critical velocity for their stability.

Contribution

It characterizes the transition of solitary wave types in a spherical condensate and links their dynamics to the Landau critical velocity for rotation.

Findings

Dipole vortices at low speeds

Jones-Roberts solitons at higher speeds

Identification of a Landau critical velocity

Abstract

The nonlinear excitations underlying the onset of rotation in a dilute Bose-Einstein condensate confined to a thin spherical shell are studied. These excitations correspond to solitary waves rotating about the sphere at constant angular speed: at low speeds they appear as dipoles of singly quantized vortices with opposite circulation, while at higher speeds they evolve into vortex-free Jones-Roberts solitons. With further increase of the angular speed, these excitations hybridize with equatorially confined modes whose azimuthal wave number is set by the sphere radius measured in units of the healing length. The propagation speed of these modes is shown to play the role of a Landau critical velocity, thereby setting the upper limiting angular speed of the entire Jones-Roberts family.