Observation of Bistable Turbulence in Quasi-Two-Dimensional Superflow

Varga, E.; Vadakkumbatt, Vaisakh; Shook, A. J.; Kim, P. H.; Davis, J. P.

doi:10.1103/physrevlett.125.025301

Cited by 16 publications

(7 citation statements)

References 45 publications

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“…In the pinning phase diagram we found that strong yet small radii potentials will pin vortices for a broader range of parameters. This may have important implications for devices utilising superfluid helium thin films [28,47], where ξ ∼ 1Å. Our results suggest that atomic defects may be superior pins to fabricated, microscale defects.…”

Section: Fall-on (Pinning)mentioning

confidence: 70%

Dynamical Mechanisms of Vortex Pinning in Superfluid Thin Films

Stockdale

Reeves

2021

Phys. Rev. Lett.

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We characterize the mechanisms of vortex pinning in a superfluid thin film described by the two-dimensional Gross-Pitaevskii equation. We consider a vortex "scattering experiment" whereby a single vortex in a superfluid flow interacts with a circular pinning potential. By an analogy with linear dielectrics, we develop an analytical hydrodynamic approximation that predicts vortex trajectories, the vortex fixed point, and the unpinning superfluid velocity beyond which the vortex cannot be trapped. We then solve the Gross-Pitaevskii equation to validate this model, and build a phase portrait of vortex pinning. We identify two different dynamical pinning mechanisms, marked by distinctive phonon emission signatures: firstly a "fall-on" regime enabled by acoustic radiation, and secondly a "pair-creation" regime, mediated by vortex dipoles nucleated within the pin. Pinning potentials with a size on the order of the healing length are found to be optimal for vortex capture. Our results will be useful in mitigating the deleterious effects of drag due to vortices in superfluid channels, in analogy to maximising supercurrents in type-II superconductors.

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Section: Fall-on (Pinning)mentioning

confidence: 70%

Dynamical Mechanisms of Vortex Pinning in Superfluid Thin Films

Stockdale

Reeves

2021

Phys. Rev. Lett.

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“…In the present work, we propose a novel architecture for superfluid optomechanics, based on engineered nanostructures allowing a better control over superfluid phonon propagation, preserving superfluid 4 He's exceptional intrinsic properties, and leading to enhanced quality factors and coupling strengths. Exploiting recent progress in quantum nanofluidics, concerning the confinement at the nanoscale of quantum fluids (liquid helium-4 [27][28][29][30][31][32][33][34] and liquid helium-3 [29,[35][36][37][38][39][40]), one can form a nanoscale cavity of typically hundreds of nm in height, and tens of µm in width defining the boundaries of a picogram or femtogram scale superfluid acoustic resonator [30][31][32]. Such superfluid acoustic resonator could be formed by means of a microsale hollow volume within a glass or silicon substrate.…”

Section: Introductionmentioning

confidence: 99%

Superfluid Optomechanics With Phononic Nanostructures

et al. 2021

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In quantum optomechanics, finding materials and strategies to limit losses has been crucial to the progress of the field. Recently, superfluid 4 He was proposed as a promising mechanical element for quantum optomechanics. This quantum fluid shows highly desirable properties (e.g. extremely low acoustic loss) for a quantum optomechanical system. In current implementations, superfluid optomechanical systems suffer from external sources of loss, which spoils the quality factor of resonators. In this work, we propose a new implementation, exploiting nanofluidic confinement. Our approach, based on acoustic resonators formed within phononic nanostructures, aims at limiting radiation losses to preserve the intrinsic properties of superfluid 4 He. In this work, we estimate the optomechanical system parameters. Using recent theory, we derive the expected quality factors for acoustic resonators in different thermodynamic conditions. We calculate the sources of loss induced by the phononic nanostructures with numerical simulations. Our results indicate the feasibility of the proposed approach in a broad range of parameters, which opens new prospects for more complex geometries.

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“…1(a,b), where He-II is confined to a thin volume enclosed by a quartz substrate (see [31] for fabrication details). Here, the resonator differs from previous designs [12,32] by using two separate circular volumes ("basins", confinement D 0 ≈ 700 nm) interconnected through a strongly confined central channel (confinement D 1 ≈ 25 or 50 nm). The nanofluidic volume is connected to a surrounding pressurised bath via four inlets.…”

mentioning

confidence: 99%

“…In the experiment the lowest attainable temperature was 0.6 K, which was used in place of the zero-temperature limit (for bulk He-II at saturated vapour pressure, ρ s /ρ > 99.99% at 0.6 K [33]). Since no measurable deviations from bulk behaviour are expected for the 700 nm confinement further than 1 mK from the transition temperature [15,29], we use the superfluid fraction determined using the fundamental mode as an in-situ thermometer calibrated against the bulk superfluid fraction calculated using the HEPAK data [34].We drive both resonances sufficiently weakly to avoid the turbulent non-linear response [32].…”

mentioning

confidence: 99%

Surface-dominated finite size effects in nanoconfined superfluid helium

Varga¹,

Undershute²,

Davis³

2022

Preprint

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Superfluid 4 He (He-II) is a widely studied model system for exploring finite-size effects in strongly confined geometries. Here we study He-II confined into mm-scale channels of 25 and 50 nm height, at arbitrarily high pressures using a nanofluidic Helmholtz resonator. We find that the superfluid density is measurably suppressed in the confined geometry from the transition temperature down to 0.6 K. Importantly, this suppression can be accounted for by roton-like thermal excitation with an energy gap of 5 K. This finding sheds light on the unexplained lack of finite-size scaling of suppression of the superfluid density. Additionally, the strong confinement allows for observation of the Kosterlitz-Thouless transition for the first time at arbitrary pressure.

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Observation of Bistable Turbulence in Quasi-Two-Dimensional Superflow

Cited by 16 publications

References 45 publications

Dynamical Mechanisms of Vortex Pinning in Superfluid Thin Films

Dynamical Mechanisms of Vortex Pinning in Superfluid Thin Films

Superfluid Optomechanics With Phononic Nanostructures

Surface-dominated finite size effects in nanoconfined superfluid helium

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