Universal Aspects of Vortex Reconnections across the BCS-BEC Crossover

TL;DR

This paper demonstrates that vortex reconnection dynamics exhibit universal behavior across the BCS-BEC crossover, including in complex, spin-imbalanced Fermi superfluids, extending previous findings from BECs and helium-4.

Contribution

It provides the first evidence that vortex reconnection universality applies across the entire BCS-BEC crossover, including in spin-imbalanced Fermi superfluids.

Findings

Reconnection dynamics follow universal scaling laws.

Universality persists in spin-imbalanced systems with unpaired fermions.

Supports the phase-driven reconnection model across different superfluid regimes.

Abstract

Reconnecting vortices in a superfluid allow for the energy transfer between different length scales and its subsequent dissipation. The present picture assumes that the dynamics of a reconnection is driven mostly by the phase of the order parameter, and this statement can be justified in the case of Bose-Einstein Condensates (BECs), where vortices have a simple internal structure. Therefore, it is natural to postulate that the reconnection dynamics in the vicinity of the reconnection moment is universal. This expectation has been confirmed in numerical simulations for BECs and experimentally for the superfluid ${}^4$He. Not much has been said about this relation in the context of Fermi superfluids. In this article we aim at bridging this gap, and we report our findings, which reveal that the reconnection dynamics conforms with the predicted universal behaviour across the entire BCS-BEC crossover. The universal scaling also survives for spin-imbalanced systems, where unpaired fermions induce a complex structure of the colliding vortices.