Universal aspects of vortex reconnections across the BCS-BEC crossover

Abstract

Reconnecting vortices in a superfluid allows 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 $^{4}\mathrm{He}$. Not much has been said about this relation in the context of Fermi superfluids. In this Letter, we aim to bridge this gap, and we report our findings, which reveal that the reconnection dynamics conforms with the predicted universal behavior 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.