Critical spin superflow in a spinor Bose-Einstein condensate

TL;DR

This paper explores the critical behavior of spin superflow in a spinor Bose-Einstein condensate, revealing how dissipation and turbulence emerge through soliton formation and magnon excitations when certain thresholds are exceeded.

Contribution

It uncovers the mechanisms of dissipation and turbulence in spin superflow, identifying critical points related to soliton generation and magnon excitations in a spinor BEC.

Findings

Damping rate increases sharply above a critical magnetic field gradient.

Dark-bright solitons are generated via modulation instability.

Transverse magnon excitations lead to spin domain formation.

Abstract

We investigate the critical dynamics of spin superflow in an easy-plane antiferromagnetic spinor Bose-Einstein condensate. Spin-dipole oscillations are induced in a trapped condensate by applying a linear magnetic field gradient and we observe that the damping rate increases rapidly as the field gradient increases above a certain critical value. The onset of dissipation is found to be associated with the generation of dark-bright solitons due to the modulation instability of the counterflow of two spin components. Spin turbulence emerges as the solitons decay because of their snake instability. We identify another critical point for spin superflow, in which transverse magnon excitations are dynamically generated via spin-exchanging collisions, which leads to the transient formation of axial polar spin domains.