Quantum vortex dipole as a probe of the normal component distribution

TL;DR

This study uses vortex dipoles in a spin-imbalanced Fermi superfluid to reveal the spatial distribution of the normal component, demonstrating their potential as probes for exotic superfluid phases at zero temperature.

Contribution

It introduces vortex dipoles as a novel, sensitive method to detect the nonuniform normal component in spin-imbalanced Fermi gases at zero temperature.

Findings

Vortex trajectories are significantly affected by spin polarization distribution.

Dipoles experience deflection, shrinking, or annihilation depending on polarization.

Vortex behavior indicates the presence of a nonuniform normal component at zero temperature.

Abstract

We investigate the dynamics of quantum vortex dipoles in a strongly interacting, spin-imbalanced Fermi superfluid at zero temperature. Using fully microscopic time-dependent density functional theory, we demonstrate that the dipole trajectory is strongly influenced by the spatial distribution of spin polarization. The resulting forces on the vortices include both longitudinal and transverse components, leading to deflection and shrinking of the dipole during propagation. For moderate polarization, vortex dipoles are deflected and lose energy, while for larger imbalances, they are rapidly annihilated. Our findings provide compelling evidence that spin-imbalanced Fermi gases contain a spatially nonuniform normal component even at zero temperature. We show that vortex dipoles serve as sensitive probes of this component, offering a route to indirectly detect exotic superfluid phases such as the Fulde-Ferrell-Larkin-Ovchinnikov state and related inhomogeneous condensates.