Observation of Quantized Circulation in Superfluid Helium

Whitmore, S.C.; Zimmermann, W.

doi:10.1103/physrev.166.181

Cited by 56 publications

(17 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, as explained in detail in Ref. [9], the modes are actually linear and perpendicular. They differ in frequency by ∆ω 0 , probably because of imperfections in the wire's cross-section or mounting.…”

Section: Experimental Backgroundmentioning

confidence: 99%

“…Our experimental setup is similar to that used in previous generations of vibrating wire experiments [8,9,13]. A brass cylinder of height 50 mm and inner radius about 1.5 mm is filled with helium.…”

Section: Experimental Backgroundmentioning

confidence: 99%

“…Since the middle has a larger vibration amplitude than the ends, it contributes more heavily to the final beat frequency. If there is one quantum of circulation on the wire below an attachment point z, and zero circulation above z, then Equation 1 still holds, with κ replaced by an effective circulation < κ > defined by [9] …”

Section: Experimental Backgroundmentioning

confidence: 99%

“…In the presence of fluid circulating around the wire, the normal modes of the wire's vibration are split, with the beat frequency revealing the circulation around the wire. This technique originated nearly forty years ago in early measurements of quantized circulation in superfluid 4 He [8,9], and was later used to measure circulation in superfluid 3 He [10]. A question that persisted through two decades of vibrating wire measurements is why intermediate circulation values are frequently observed.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Smooth vortex precession in superfluid4He

2001

View full text Add to dashboard Cite

We have measured a precessing superfluid vortex line, stretched from a wire to the wall of a cylindrical cell. By contrast to previous experiments with a similar geometry, the motion along the wall is smooth. The key difference is probably that our wire is substantially off center. We verify several numerical predictions about the motion, including an asymmetry in the precession signature, the behavior of pinning events, and the temperature dependence of the precession.

show abstract

Section: Experimental Backgroundmentioning

confidence: 99%

Section: Experimental Backgroundmentioning

confidence: 99%

Section: Experimental Backgroundmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Smooth vortex precession in superfluid4He

2001

View full text Add to dashboard Cite

show abstract

“…Trapped circulation alters the wire's vibrational normal modes and splits the fundamental frequency [9,10], causing the plane of vibration to precess. A vortex can extend along the entire wire or along only a portion.…”

mentioning

confidence: 99%

Depinning of a superfluid vortex line by Kelvin waves

2001

View full text Add to dashboard Cite

We measure the interaction of a single superfluid vortex with surface irregularities. While vortex pinning in superconductors usually becomes weaker at higher temperatures, we find the opposite behavior. The pinning steadily increases throughout our measurement range, from 0.15Tc to over 0.5Tc. We also find that moving the other end of the vortex decreases the pinning, so we propose Kelvin waves along the vortex as a depinning mechanism.PACS numbers: 67.40.Vs, 74.60.GePinning sites can trap vortices in a variety of systems. In superconductors, where vortex motion leads to nonzero resistance, a vast amount of work has been devoted to preventing such motion by introducing defects. Experimental work has shown that defects comparable in size to the vortex core make effective pin centers, and that straight [1] or splayed [2] line defects can increase the pin strength. Yet the mechanisms by which vortices interact with pin sites remain unresolved. Experimentally, pinning in superconductors becomes weaker as temperature increases, in accord with the general assumption that depinning occurs through thermal activation over local energy barriers. In some materials, a constant rate of vortex motion at low temperature indicates a crossover to quantum tunneling between pin sites [3]. No experiments have been able to probe the actual interactions. Similar issues appear in studies of neutron stars [4], where vortex pinning or friction could account for angular momentum irregularities [5].Here we report studies of a single vortex line in superfluid helium. We observe a steady increase of pinning as temperature increases, for 0.15 < T /T c < 0.6, and suggest that this unusual temperature dependence comes from the interaction of the pin site with oscillations along the vortex line. Studying one vortex rather than a sizeable collection simplifies some of the issues in pinning. Helium is also unusual in that the pinning occurs only at the end of the vortex, so our vortex interacts with a single pin site. Surface pinning dominates in superconductors as well for very clean samples [6,7] or those with surface structures such as magnetic dots [8].Our measurements use a brass cylinder, 50 mm long and filled with liquid helium. A fine superconducting wire, about 12 µm diameter, is stretched along the cell, displaced from the cylinder's axis by about 0.8 mm. The data reported here come from two cells, one drilled with inner diameter 2.9 mm (cell A) and the other reamed to diameter 3.1 mm (cell B). The walls of cell B appear smoother. A pumped 3 He cryostat can cool the cell to 300 mK. We apply a 250 G field perpendicular to the wire. A current pulse of a few milliamperes through the wire excites the wire's vibration by a Lorentz force. The ensuing motion in the magnetic field induces an emf across the wire, which we amplify and digitize.In the presence of fluid circulation, vorticity can become trapped on the wire. Trapped circulation alters the wire's vibrational normal modes and splits the fundamental frequency [9,10], causing the plane...

show abstract

Introduction to Topological Quantum Numbers

Thouless

Aspects Topologiques De La Physique en Basse Dimension. Topological Aspects of Low Dimensional Systems

View full text Add to dashboard Cite

Observation of Quantized Circulation in Superfluid Helium

Cited by 56 publications

References 17 publications

Smooth vortex precession in superfluid4He

Smooth vortex precession in superfluid4He

Depinning of a superfluid vortex line by Kelvin waves

Introduction to Topological Quantum Numbers

Contact Info

Product

Resources

About