Dynamics of Polar-Core Spin Vortices in Inhomogeneous Spin-1 Bose-Einstein Condensates

TL;DR

This paper investigates the dynamics of polar-core spin vortices in inhomogeneous spin-1 Bose-Einstein condensates, revealing how they accelerate and oscillate due to spin-changing collisions and trap geometry.

Contribution

It introduces a simplified model for PCV dynamics in inhomogeneous condensates and uncovers novel behaviors like radial acceleration and long-lived oscillations.

Findings

PCVs accelerate towards the condensate boundary in harmonic traps.

Oscillations of PCVs occur around trap centers with emission and reabsorption of spin waves.

The dynamics depend on trap tightness and quadratic Zeeman energy.

Abstract

In the easy-plane phase, a ferromagnetic spin-1 Bose-Einstein condensate is magnetized in a plane transverse to the applied Zeeman field. This phase supports polar-core spin vortices (PCVs), which consist of phase windings of transverse magnetization. Here we show that spin-changing collisions cause a PCV to accelerate down density gradients in an inhomogeneous condensate. The dynamics is well-described by a simplified model adapted from scalar systems, which predicts the dependence of the dynamics on trap tightness and quadratic Zeeman energy. In a harmonic trap, a PCV accelerates radially to the condensate boundary, in stark contrast to the azimuthal motion of vortices in a scalar condensate. In a trap that has a local potential maximum at the centre, the PCV exhibits oscillations around the trap centre, which persist for a remarkably long time. The oscillations coincide with the emission and reabsorption of axial spin waves, which reflect off the condensate boundary.