Shear Flow and Kelvin-Helmholtz Instability in Superfluids
Rob Blaauwgeers, Vladimir B. Eltsov, Girgl Eska, Antti P. Finne, Richard P. Haley, M. Krusius, Jaakko J. Ruohio, Ladislav Skrbek, Grigori E. Volovik
Low Temperature Laboratory, Helsinki University of Technology, P.O. Box 2200, 02015 HUT, Finland
A shear-flow instability between two fluid layers occurs in many different natural phenomena. The most common example is the creation of waves on water by wind. In the ideal case of inviscid and incompressible liquids this phenomenon is known as the Kelvin-Helmholtz (KH) instability. We present an experiment where we stabilize the boundary between 3He-A and 3He-B in a rotating cylindrical container. On starting a slow acceleration, A phase vortices, which have low critical velocity, form immediately, while at this point no vortices are detected in the B phase. We thus have two superfluids sliding over each other, and for the first time created the ideal conditions of the KH instability. The onset of the instability, detected through a burst-like injection of vorticity in the B phase, is in perfect agreement with theory.
Critical thickness of A-B phase transition in superfluid 3He film
Kenji Kawasaki, Tomohiro Yoshida, Hideo Yano, Osamu Ishikawa, Tohru Hata
Graduate School of Science, Osaka City University, Osaka 558-8585, Japan
The anisotropic A phase becomes stable in thin film because of the axial symmetry. From NMR measurements with 0.8 mm and 1.1 mm superfluid 3He film, we observed A phase even at low pressures and we have obtained the critical thickness d for A-B phase transition occurrence in wide pressure range. This thickness is the ratio of real film thickness to temperature dependent coherence length at which A-B transition occurs. This d depended nearly linearly on pressure p [MPa] as d =13.7+7.37p, which was estimated about 8 in the weak coupling approximation. It is estimated that in the superfluid 3He film thinner than 0.3 mm only A phase appears in all pressures below the superfluid transition temperature Tc.
The Shapiro Effect using a superfluid 3He weak link
Raymond W. Simmonds, Alexei Marchenkov, James C. Davis, Richard E. Packard
Department of Physics, University of California, Berkeley, 366 Le Conte, Berkeley, CA 94720
In the original paper predicting the superconducting Josephson effect, Josephson proposed that if, in addition to a constant voltage bias, a high frequency ac voltage is applied across a superconducting Josephson junction, the super-currents will exhibit characteristic changes. Shapiro first observed these predicted phenomena appearing as ``steps" in the current-voltage curves of superconducting Josephson junctions. These results yielded a strong confirmation of the superconducting Josephson relations. For over thirty years much effort has been focused on searches for equivalent phenomena using a single small orifice, both in liquid 4He and in liquid 3He. We describe the first successful observation of the ``superfluid Shapiro effect" using a superfluid 3He weak link array. Ironically, this result has only appeared after the direct verification of Josephson's relations for a superfluid 3He weak link.
Kinetic growth properties of the interface of phase-separated 3He-4He liquid mixtures
Haruka Abea, Serguei N. Burmistrovb, Takeo Satoha
aPhysics Department, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
bKurchatov Institute, Moscow 123182, Russia
The kinetic growth properties of the interface of phase-separated 3He-4He mixtures play an important role in the nucleation process from the supersaturated state. We have determined the kinetic growth coefficient of the interface, xw, by measuring the transmission of sound(9, 14 and 32MHz) through the interface within the temperature range 10mK-200mK. It is found that xw starts increasing with the decrease of temperature, i.e., below ~ 70mK for 9MHz, below ~ 100mK for 14MHz, and below ~ 160mK for 32MHz. The whole data of this increasing behavior can be fitted very well as xw µ w5/2/T3. We present the data including the pressure dependence and give theoretical discussions.
Condensation of 3He and Reentrant Superfluidity in 3He-4He Mixture Films on H2
G.A. Csáthy, E. Kim, M.H.W. Chan
Pennsylvania State University, University Park, PA 16802, USA
The superfluid response of submonolayer 3He-4He mixture films adsorbed onto H2 and Au substrates has been investigated by means of torsional oscillator technique. On the Au substrate the introduction of 3He into the superfluid film suppresses the superfluid onset temperature monotonically. In contrast, on the H2 substrate superfluidity is initially suppressed, then enhanced, and suppressed again with increasing 3He coverage. This behavior leads to reentrant superfluidity in the limit of zero temperature. We attribute this novel behavior to the condensation of 3He confined near the free surface of the superfluid 4He film into a self-bound 2D liquid.