We compute the orbital angular momentum L_{z} of an s-wave paired superfluid in the presence of an axisymmetric multiply quantized vortex. For vortices with a winding number |k|>1, we find that in the weak-pairing BCS regime, L_{z} is significantly reduced from its value ℏNk/2 in the Bose-Einstein condensation (BEC) regime, where N is the total number of fermions. This deviation results from the presence of unpaired fermions in the BCS ground state, which arise as a consequence of spectral flow along the vortex subgap states. We support our results analytically and numerically by solving the Bogoliubov-de Gennes equations within the weak-pairing BCS regime.We compute the orbital angular momentum L_{z} of an s-wave paired superfluid in the presence of an axisymmetric multiply quantized vortex. For vortices with a winding number |k|>1, we find that in the weak-pairing BCS regime, L_{z} is significantly reduced from its value ℏNk/2 in the Bose-Einstein condensation (BEC) regime, where N is the total number of fermions. This deviation results from the presence of unpaired fermions in the BCS ground state, which arise as a consequence of spectral flow along the vortex subgap states. We support our results analytically and numerically by solving the Bogoliubov-de Gennes equations within the weak-pairing BCS regime.

arXiv:1702.04361Physical Review LettersAug 8, 201720 citations

Origin and evolution of the multiply-quantised vortex instability

Sam Patrick, August Geelmuyden, Sebastian Erne +2 more

We show that the dynamical instability of quantum vortices with more than a single quantum of angular momentum results from a superradiant bound state inside the vortex core. Our conclusion is supported by an analytic WKB calculation and numerical simulations of both linearised and fully non-linear equations of motion for a doubly-quantised vortex at the centre of a circular bucket trap. In the late stage of the instability, we reveal a striking novel behaviour of the system in the non-linear regime. Contrary to expectation, in the absence of dissipation the system never enters the regime of two well-separated phase defects described by Hamiltonian vortex dynamics. Instead, the separation between the two defects undergoes modulations which never exceed a few healing lengths, in which compressible kinetic energy and incompressible kinetic energy are exchanged. This suggests that, under the right conditions, pairs of vortices may be able to form meta-stable bound states.We show that the dynamical instability of quantum vortices with more than a single quantum of angular momentum results from a superradiant bound state inside the vortex core. Our conclusion is supported by an analytic WKB calculation and numerical simulations of both linearised and fully non-linear equations of motion for a doubly-quantised vortex at the centre of a circular bucket trap. In the late stage of the instability, we reveal a striking novel behaviour of the system in the non-linear regime. Contrary to expectation, in the absence of dissipation the system never enters the regime of two well-separated phase defects described by Hamiltonian vortex dynamics. Instead, the separation between the two defects undergoes modulations which never exceed a few healing lengths, in which compressible kinetic energy and incompressible kinetic energy are exchanged. This suggests that, under the right conditions, pairs of vortices may be able to form meta-stable bound states.

arXiv:2111.02567Nov 4, 20210 citations

QUANTUM VORTICES IN A FERMION SYSTEM

Л. П. Рапопорт, A.G. Krylovetskii

Journal of Experimental and Theoretical PhysicsDec 1, 19620 citations

Vortices and superfluidity in a strongly interacting Fermi gas

Martin W. Zwierlein, J. R. Abo-Shaeer, André Schirotzek +2 more

arXiv:cond-mat/0505635NatureJun 1, 20051,016 citations

Rotating mixed He3−He4 nanodroplets

Martí Pi, Francesco Ancilotto, José María Escartín +2 more

Mixed $^{3}\mathrm{He}\ensuremath{-}^{4}\mathrm{He}$ droplets may acquire angular momentum during their passage through the nozzle of the experimental apparatus, cooling down and undergoing isotopic segregation, developing a $^{3}\mathrm{He}$ crust surrounding a superfluid $^{4}\mathrm{He}$ core. Within density functional theory, we investigate their stability and the relations between their angular momenta and their shapes. We uncover a variety of behaviors where the interplay between the superfluid $^{4}\mathrm{He}$ core and the normal-fluid $^{3}\mathrm{He}$ coating leads to a scenario that both bears analogies with viscous rotating drops and displays new features such as configurations with a fissioned or three-lobed $^{4}\mathrm{He}$ core, or with multiply charged vortices.Mixed $^{3}\mathrm{He}\ensuremath{-}^{4}\mathrm{He}$ droplets may acquire angular momentum during their passage through the nozzle of the experimental apparatus, cooling down and undergoing isotopic segregation, developing a $^{3}\mathrm{He}$ crust surrounding a superfluid $^{4}\mathrm{He}$ core. Within density functional theory, we investigate their stability and the relations between their angular momenta and their shapes. We uncover a variety of behaviors where the interplay between the superfluid $^{4}\mathrm{He}$ core and the normal-fluid $^{3}\mathrm{He}$ coating leads to a scenario that both bears analogies with viscous rotating drops and displays new features such as configurations with a fissioned or three-lobed $^{4}\mathrm{He}$ core, or with multiply charged vortices.

arXiv:2003.03306Physical review. B./Physical review. BAug 7, 20207 citations

^{3}\mathrm{He}

crust surrounding a superfluid

^{4}\mathrm{He}

core. Within density functional theory, we investigate their stability and the relations between their angular momenta and their shapes. We uncover a variety of behaviors where the interplay between the superfluid

^{4}\mathrm{He}

core and the normal-fluid

^{3}\mathrm{He}

coating leads to a scenario that both bears analogies with viscous rotating drops and displays new features such as configurations with a fissioned or three-lobed

^{4}\mathrm{He}

core, or with multiply charged vortices.