Browsing by Author "Tvalashvili, G. K."

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  • Coupling of zero sound to the real squashing mode in rotating 3B
    (1989) Salmelin, Riitta; Pekola, Jukka P.; Manninen, A. J.; Torizuka, K.; Berglund, M. P.; Kyynäräinen, J. M.; Lounasmaa, O. V.; Tvalashvili, G. K.; Magradze, O. V.; Varoquaux, E.; Avenel, O.; Mineev, V. P.
     School of Science | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Rotation of superfluid 3B in an magnetic field enhances the coupling of the nonzero mJ substrates of the real squashing collective mode to the zero sound, and the fivefold line splitting becomes observable even when H is parallel to Ω and to the direction of sound propagation. Equilibrium vortex lattices and vortex-free states can be distinguished by their characteristic absorption spectra. The dependence of the sound attenuation on the angular velocity in magnetic fields up to 32 mT is reported; the data are qualitatively compared with theory.
  • Coupling of zero sound to the real squashing mode in rotating 3He-B
    (1989-08-07) Salmelin, R. H.; Pekola, J. P.; Manninen, A. J.; Torizuka, K.; Berglund, M. P.; Kyynäräinen, J. M.; Lounasmaa, O. V.; Tvalashvili, G. K.; Magradze, O. V.; Varoquaux, E.; Avenel, O.; Mineev, V. P.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Rotation of superfluid B3 in an magnetic field enhances the coupling of the nonzero mJ substrates of the real squashing collective mode to the zero sound, and the fivefold line splitting becomes observable even when H is parallel to and to the direction of sound propagation. Equilibrium vortex lattices and vortex-free states can be distinguished by their characteristic absorption spectra. The dependence of the sound attenuation on the angular velocity in magnetic fields up to 32 mT is reported; the data are qualitatively compared with theory.
  • Elementary Steps on the 4He Crystal Interface Probed by 3He Atoms
    (1999-12-06) Tsepelin, V.; Saramäki, J. P.; Babkin, A. V.; Hakonen, P. J.; Hyvönen, J. J.; Luusalo, R. M.; Parshin, A.Ya.; Tvalashvili, G. K.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The growth dynamics of c facets, governed by individual Frank-Read type of sources, has been studied at millikelvin temperatures in the presence of small concentrations of 3He atoms in the liquid. We find that in the spiral growth regime, interaction of 3He atoms with moving elementary steps on the surface results in additional friction. Our results are compared with theory, where high-frequency (ω ≥ T/ℏ) zero-point oscillations of the steps are taken into account. There is a good agreement if we assume the amplitude of these oscillations ξ ≈ 5 nm.
  • Wave acoustics for propagation of ultrasound along a vortex array in superfluid 3A
    (1992-05-01) Sonin, E. B.; Torizuka, K.; Kyynarainen, J. M.; Pekola, J. P.; Tvalashvili, G. K.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    A wave-acoustics theory has been developed to describe the propagation of zero sound parallel to vortex lines in rotating A3. We show that a diffraction shadow is formed in which the wave amplitude is suppressed by interference around vortices. This phenomenon contributes to the experimentally observed effect of rotation on the sound amplitude and exceeds the attenuation at large core radii. The dependence of the diffraction contribution on the angular velocity changes drastically at the transition from vortices with a finite core to coreless vortices when the magnetic field is decreased to zero. We derive conditions for the applicability of the effective-medium theory and the classical geometrical acoustic method in describing sound propagation along vortices.
  • Wave acoustics for propagation of ultrasound along a vortex array in superfluid 3He-A
    (1992) Sonin, E. B.; Torizuka, K.; Kyynäräinen, J. M.; Pekola, Jukka P.; Tvalashvili, G. K.
     School of Science | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    A wave-acoustics theory has been developed to describe the propagation of zero sound parallel to vortex lines in rotating 3He-A. We show that a diffraction "shadow" is formed in which the wave amplitude is suppressed by interference around vortices. This phenomenon contributes to the experimentally observed effect of rotation on the sound amplitude and exceeds the attenuation at large core radii. The dependence of the diffraction contribution on the angular velocity changes drastically at the transition from vortices with a finite core to coreless vortices when the magnetic field is decreased to zero. We derive conditions for the applicability of the effective-medium theory and the classical geometrical acoustic method in describing sound propagation along vortices.