Topological defect formation in quenched ferromagnetic Bose-Einstein condensates

TL;DR

This paper investigates the formation of topological defects, such as spin vortices and domain walls, during a quantum phase transition in ferromagnetic spin-1 Bose-Einstein condensates, highlighting the influence of initial noise and quench protocols.

Contribution

It demonstrates the dependence of defect formation on initial noise conditions and quench methods, and draws an analogy with vortex formation in scalar BECs.

Findings

Spontaneous formation of spinor domain walls and polar-core spin vortices.

Defect formation is highly sensitive to initial noise distribution.

The dynamics depend on how the magnetic field is varied.

Abstract

We study the dynamics of the quantum phase transition of a ferromagnetic spin-1 Bose-Einstein condensate from the polar phase to the broken-axisymmetry phase by changing magnetic field, and find the spontaneous formation of spinor domain walls followed by the creation of polar-core spin vortices. We also find that the spin textures depend very sensitively on the initial noise distribution, and that an anisotropic and colored initial noise is needed to reproduce the Berkeley experiment [Sadler et al., Nature 443, 312 (2006)]. The dynamics of vortex nucleation and the number of created vortices depend also on the manner in which the magnetic field is changed. We point out an analogy between the formation of spin vortices from domain walls in a spinor BEC and that of vortex-antivortex pairs from dark solitons in a scalar BEC.