Critical Energy Dissipation in a Binary Superfluid Gas by a Moving Magnetic Obstacle

TL;DR

This paper investigates how a magnetic obstacle induces energy dissipation in a two-component superfluid gas, revealing spin-wave generation and half-quantum vortex formation at critical oscillation frequencies.

Contribution

It demonstrates the transition from spin-wave emission to half-quantum vortex shedding and identifies critical velocities for vortex creation using oscillating and pulsed obstacle methods.

Findings

Spin-wave excitations occur above a critical oscillation frequency.

Half-quantum vortices are generated at higher frequencies when the obstacle causes density perturbations.

Two critical velocities for creating HQVs with different core magnetizations are identified.

Abstract

We study the critical energy dissipation in an atomic superfluid gas with two symmetric spin components by an oscillating magnetic obstacle. Above a certain critical oscillation frequency, spin-wave excitations are generated by the magnetic obstacle, demonstrating the spin superfluid behavior of the system. When the obstacle is strong enough to cause density perturbations via local saturation of spin polarization, half-quantum vortices (HQVs) are created for higher oscillation frequencies, which reveals the characteristic evolution of critical dissipative dynamics from spin-wave emission to HQV shedding. Critical HQV shedding is further investigated using a pulsed linear motion of the obstacle, and we identify two critical velocities to create HQVs with different core magnetization.