Singular Vortex in Narrow Cylinders of Superfluid 3He-A Phase

Motivated by the on-going rotating cryostat experiments in ISSP, Univ. of Tokyo, we explore the textures and vortices in superfluid 3He-A phase confined in narrow cylinders, whose radii are R=50mum and 115mum. The calculations are based on the Ginzburg-Landau (GL) framework, which fully takes into account the orbital (l-vector) and spin (d-vector) degrees of freedom for chiral p-wave pairing superfluid. The GL free energy functional is solved numerically by using best known GL parameters appropriate for the actual experimental situations at P=3.2MPa and H=21.6mT. We identify the ground state l-vector configuration as radial disgyration (RD) texture with the polar core both at rest and low rotations and associated d-vector textures for both narrow cylinder systems under high magnetic fields. The RD which has a singularity at center, changes into Mermin-Ho texture above the critical rotation speed which is determined precisely, providing an experimental check for own proposal.Comment: 22 pages, 12 figure

Observation of Coherent Precession of Magnetization in Superfluid 3He A-phase

We report the first observation of coherent quantum precession of magnetization (CQP) in superfluid 3He-A in aerogel. The coherent precession in bulk 3He A-phase is unstable due to the positive feedback of spin supercurrent to the gradient of phase of precession. It was predicted that the homogeneous precession will be stable if the orbital momentum of 3He-A could be oriented along the magnetic field. We have succeeded to prepare this configuration by emerging 3He in uniaxially-deformed anisotropic aerogel. The dissipation rate of coherent precession states in aerogel is much larger then one in bulk 3He-B. We propose a mechanism of this dissipation.Comment: 4 pages, 4 figure

Texture and Vortex of Rotating Superfluid 3He-A in Parallel-plate Geometry

Unique types of textures and vortices of superfluid 3He in restricted geometries have been discussed. We investigated cw-NMR in rotating 3He A-phase in parallel plate geometries with gaps of 12.5 μm at 3.05 MPa. We observed a very sharp spectrum at rest which had shifted negatively as f=f L−0.93f A(T), where f A(T) is the full transverse dipole shift in A-phase. The large negative shift of 0.93f A(T) indicates that l ⊥ d. When we rotated the sample with rotation speed Ω faster than the critical Ω Fr, a new satellite signal appeared nearly at f L. The satellite signal intensity increased with increasing Ω, reached a maximum at Ω c and slowly decreased up to the maximum Ω of 2π rad/s. When Ω decreased from the maximum speed, the satellite signal rapidly decreased and disappeared at 5.5 rad/s down to zero rad/s. We measured the temperature dependence of the satellite signal intensity, Ω Fr and Ω c. We propose a model for the satellite signal, which is attributed to spin wave in Fréedericksz transition region induced by the counter flow. We also compare the satellite signal with Kee and Maki’s bound pair of HQV

Coherent precession of magnetization in superfluid 3He A-phase in aerogel

International audienceThe coherent precession in bulk 3He A-phase is unstable due to the positive feedback of spin supercurrent to the gradient of phase of precession. It was predicted that the homogeneous precession will be stable if the orbital momentum could be oriented along the magnetic field. [7] We have found that the orbital part of order parameter in 3He A-phase immersed in aerogel orients along the direction of aerogel axial squeezing. By this method we have oriented the orbital momentum of 3He A-phase along the magnetic field and studied non-linear NMR properties. By cw-NMR we have succeeded to form the state with Coherent Precession in 3He A-phase (CP-A), which is analog of Homogeneous Precession Domain (HPD) in 3He B-phase. We have found that the dissipation of CP-A and HPD in aerogel is much larger than in bulk superfluid 3He and depends from sample to sample. We propose a model to explain enhancement of the dissipation in CP-A, which takes into account the spin diffusion of inhomogeneous magnetization created by fluctuations of the condensation energy of Cooper pair in aerogel