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HPD and Superfluid Hydrodynamics

Explore the interaction of superfluid hydrodynamics with vortices, including vortex motion, field tilting effects, and cosmic-like solitons. Understand the implications for gyroscopes, temperature stability, and heat leaks in superfluid systems.

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HPD and Superfluid Hydrodynamics

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  1. HPD and Superfluid Hydrodynamics Yury Mukharsky COSLAB-2004

  2. Low Temperature Laboratory, Helsinki University of TechnologyKapitza InstituteLandau InstituteIoffe Institute J. S. Korhonen, Y. Kondo, M. Krusius, Ü. Parts, E. V. Thuneberg Yu. M. Bunkov, V. V. Dmitriev G. E. Volovik E. B. Sonin COSLAB-2004

  3. H n n l l v In the HPD Counterflow suppresses the HPD. HPD and counterflow • Magnetic field  anisotropy of rs interaction with vs. Minimized at equilibrium by adjusting R. COSLAB-2004

  4. Interaction of HPD with vortices. COSLAB-2004

  5. Vortex motion • Vortex core rotates and rocks. • Rocking motion causes the dissipation j h H b COSLAB-2004

  6. Interaction of HPD with vortices. When vortex end are pinned – twisting. Twisted vortex is more rigid and rocks less. When the vortex move – the ends are free. COSLAB-2004

  7. Effect of field tilting • Tilting the field orients the vortex: • No twisting • Reduced rocking motion. • Smaller dissipation. COSLAB-2004

  8. If we twist less? • Rocking motion is less suppressed. • Difference in absorption smaller • Shorted HPD – weaker twist. COSLAB-2004

  9. Cosmic-like soliton. Connects two half-quantum vortices. COSLAB-2004

  10. Olivier Avenel, Eric Varoquaux CEA-DRECAM, Service de Physique de l'Etat Condense, Centre d'Etudes de Saclay, France CNRS-Laboratoire de Physique des Solides, Universite Paris-Sud, Orsay, France COSLAB-2004

  11. (H=0)=7 mm SD x The cell: • Weak link: • 198 0.10x0.10 mm holes separated by 2 mm in SiliconNitride membrane ~0.1 mm thick.Membrane: 75x60 mm, Ra=16 mm, R k=0.03 mm • Part of the membrane where edge effects can be strong is highlighted with yellow. xs COSLAB-2004

  12. Flexible Diaphragm Cap. plate Orifice Pos. Sensor The pressure across the orifice is proportional to the diaphragm displacement plus electrostatic pressure. The phase across the orifice is proportional to the integral of pressure: Amplitude of phase oscillations  amplitude of diaphragm. C d P f L (orifice) 1 P el L 2 Measurements Technique. • Flexible diaphragm+Fluid inertia=Resonator • Position of the diaphragm (equivalent to the charge of the capacitor) is recorded. The current through the orifice/parallel path is determined as derivative of the diaphragm location. COSLAB-2004

  13. Flexible Diaphragm Cap. plate Cap. plate. Orifice Pos. Sensor W f kx P el Measurements Technique - rotation. • Rotation results in the circulation in the sensing loop. Thus the rotation changes phase drop across the weak link. Earth - rotating platform. Change in rotation - reorient apparatus relative to the Earth. Effect has been calibrated in 4He experiments: with 4.9 cm2 two-turn loop we use, the Earth rotation produces circulation ~0.85 k3. COSLAB-2004

  14. k4 Data Analysis Large amplitude frequency (f0) COSLAB-2004

  15. Precision in the bias. COSLAB-2004

  16. Bias does not change much after going through Tc, if it does not jump by k3/2 We assign bias ~0 to the case which happens more often (see below). p-shift. T effect explains most of the scatter show on the picture to the left (local overheating of the inner cell while at nominally stable T). Bias at fixed T, P and magnetic field. COSLAB-2004

  17. p-shifted states. COSLAB-2004

  18. p-solitons? Salomaa-Volovik, 1988 Vortex? Explanations? Very large energy. Bind cores of double-core vortex. Thought to be unstable in bulk (are they?) COSLAB-2004

  19. 100 gauss Coils Why soliton? COSLAB-2004

  20. Heat leak to inner cell, due, for example to heat release from Stycast or eddy heating in silver increases fountain pressure there and causes normal current flow from the inner cell and counterflow of superfluid into it. vs Q vn Q Explanation of T-dependence Ag Stycast • As observed, the circulation should diverge towards Tc. • Change of the sign (weak), however, remains unexplained. COSLAB-2004

  21. Summary • A number (~8) of different current-phase relations (CPR) are observed. • Under certain conditions most of these relations are observed shifted by p. • The shift appears to be unrelated to the shape of the CPR and does not change when CPR changes. • We argue that the most probable cause is a cosmic-like soliton(s) crossing the sensing loop. • Temperature dependence of the trapped circulation can be explained by thermomechanical effects. • This has important implication for superfluid gyroscopes – heat leaks and temperature stability become important. • It appears that there is no remnant vorticity in the cell. COSLAB-2004

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