Splitting instability of a doubly quantized vortex in superfluid Fermi gases

TL;DR

This paper studies the splitting instability of doubly-quantized vortices in superfluid Fermi gases across the BEC-BCS crossover, revealing different mechanisms and enhanced instability in the crossover regime through theoretical and numerical analysis.

Contribution

It provides a comprehensive analysis of vortex splitting mechanisms across the BEC-BCS crossover, including phonon emission and the effects of temperature, imbalance, and dimensionality.

Findings

Vortex splitting via phonon emission in BEC limit

Enhanced instability and phonon emission in crossover regime

Observation of spiraling phonon patterns due to superradiance

Abstract

The splitting instability of a doubly-quantized vortex in the BEC-BCS crossover of a superfluid Fermi gas is investigated by means of a low-energy effective field theory. Our linear stability analysis and non-equilibrium numerical simulations reveal that the character of the instability drastically changes across the crossover. In the BEC-limit, the splitting of the vortex into two singly-quantized vortices occurs through the emission of phonons, while such an emission is completely absent in the BCS-limit. In the crossover-regime, the instability and phonon emission are enhanced, and the lifetime of a doubly-quantized vortex becomes minimal. The emitted phonon can be observed as a spiraling pattern amplified due to the rotational superradiance, known as a mechanism to carry away energy and angular momentum from a spinning black hole. We also investigate the influence of temperature, population imbalance, and three-dimensional effects.