Generating Giant Vortex in a Fermi Superfluid via Spin-Orbital-Angular-Momentum Coupling

TL;DR

This paper demonstrates the creation of giant vortices in Fermi superfluids using spin-orbital-angular-momentum coupling, revealing a new mechanism for vortex stabilization and opening avenues for exploring topological defects.

Contribution

It introduces a novel mechanism for stabilizing giant vortices in Fermi superfluids via SOAM coupling, expanding the understanding of superfluid phases and topological defects.

Findings

Giant vortices with sizes comparable to laser beam waist are stabilized in Fermi superfluids.

The vortex core structures are tunable, offering new experimental control.

The mechanism is analogous to the Fulde-Ferrell state induced by spin-orbit coupling.

Abstract

Spin-orbital-angular-momentum (SOAM) coupling has been realized in recent experiments of Bose-Einstein condensates [Chen et al., Phys. Rev. Lett. 121, 113204 (2018) and Zhang et al., Phys. Rev. Lett. 122, 110402 (2019)], where the orbital angular momentum imprinted upon bosons leads to quantized vortices. For fermions, such an exotic synthetic gauge field can provide fertile ground for fascinating pairing schemes and rich superfluid phases, which are yet to be explored. Here we demonstrate how SOAM coupling stabilizes vortices in Fermi superfluids through a unique mechanism that can be viewed as the angular analog to that of the spin-orbit-coupling-induced Fulde-Ferrell state under a Fermi surface deformation. Remarkably, the vortex size is comparable with the beam waist of Raman lasers generating the SOAM coupling, which is typically much larger than previously observed vortices in Fermi superfluids. With tunable size and core structure, these giant vortex states provide unprecedented experimental access to topological defects in Fermi superfluids.