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  • 1
    Electronic Resource
    Electronic Resource
    Mechanism for acoustic leakage in surface-acoustic wave resonators on rotated Y-cut lithium tantalate substrate (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 2683-2685 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We discuss an acoustic loss mechanism in surface-acoustic wave resonators on 36° YX-cut lithium tantalate substrate. Recent acoustic field scans performed with an optical Michelson interferometer reveal a spatially asymmetric acoustic field atop the busbars of a resonator, giving rise to acoustic beams which escape the resonator area and lead to undesired losses. Here, we link the phenomenon with the inherent crystalline anisotropy of the substrate: the shape of the slowness curves and the asymmetry of the polarization for leaky surface-acoustic waves, propagating at an angle with respect to the crystal X-axis. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.125117
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  • 2
    Electronic Resource
    Electronic Resource
    Surface acoustic wave impedance element filters for 5 GHz (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 142-144 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Surface acoustic wave (SAW) impedance element filter prototypes operating in the 5 GHz range are designed, fabricated, and characterized. The patterning is carried out using direct-writing electron-beam lithography and the lift-off technique. The periodicity p of the resonators in the filters for the 5 GHz regime is on the order of 400 nm. Despite the nonideal finger profile, a low minimum insertion loss of 6.5 dB and a flat passband are measured. Our results suggest that SAW technology itself presents no fundamental physical limitations for its extension into the 5 GHz range. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.124300
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  • 3
    Electronic Resource
    Electronic Resource
    Monopoles in the rotating superfluid helium-3 A–B interface (1987)
    [s.l.] : Nature Publishing Group
    Nature 326 (1987), S. 367-370 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The superfluid phase boundary between 3He-A and 3He-B also serves to provide a unique analogy to the cosmic domain walls1*2 that are believed to have precipitated between regions of the early Universe3 in different vacuum states. Hence the proposed experiments on the superfluid 3He A-B interface ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/326367a0
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  • 4
    Electronic Resource
    Electronic Resource
    Superfluid 3 He in rotation (1986)
    [s.l.] : Nature Publishing Group
    Nature 324 (1986), S. 333-340 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Experiments on vortices in rotating superfluid 3He have revealed phenomena which have not been observed in any other quantum liquid and have implications in fields beyond low-temperature physics. In 3He-A, vorticity may be supported by a continuous winding of the order ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/324333a0
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  • 5
    Electronic Resource
    Electronic Resource
    Evidence for a surface state with broken symmetry in3He-B from ROTA experiments at Helsinki (1989)
    Springer
    Journal of low temperature physics 75 (1989), S. 209-241 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract An unusual, newly observed, rotation-direction-dependent parity effect in nuclear magnetic resonance (NMR) experiments on rotating3He-B in a state void of vortices is here first explained in terms of the broken time-inversion symmetry (T) for the surface layer of the3He-B. Two possible types of such surface structures, both with brokenT symmetry, for superfluid3He-B near the wall of the container are consistent with properties of the parity effect: one has superfluid A phase on the3He-B surface, while the other one is characterized by a nonzero counterflow of the spin componentsS=0 andS=+-1 of the superfluid along the normal to the wall, but with the total mass supercurrent and the total spin supercurrent into the wall vanishing identically. The first surface structure is in better agreement with details of the experiment and our numerical results, which demonstrate, for the first time, absolute stability of an A-phase layer on the3He-B boundary in a certain region of the phenomenological parameters for the surface tension. We find it also possible for a first-order surface-“wetting” transition to occur by the A-phase layer between two different A-phase states: one with little A phase, the other with well developed A phase. We estimate the magnitude of the new surface-orientating effects by comparing the NMR data with computed spin-wave spectra. New types of point vortices on the surface, boojums, are possible for the3He-B with superfluid A phase on the boundary: unlike the usual boojums on the surface of3He-A, only these novel boojums on the3He-B surface display isolated half-integer quanta of superfluid circulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00681910
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  • 6
    Electronic Resource
    Electronic Resource
    NMR and axial magnetic field textures in stationary and rotating superfluid3He-B (1989)
    Springer
    Journal of low temperature physics 76 (1989), S. 225-283 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have performed NMR measurements on the flare-out texture of superfluid3He-B in a cylindrical container of 5 mm diameter in axial magnetic fields of 28.4 and 56.9 mT. The transverse cw NMR spectra have been analyzed both with respect to their overall shape and the spin-wave absorption peaks close to the Larmor frequency. Our analysis of the stationary state spectra, based on texture computations, yields the longitudinal resonance frequency v L (T), the magnetic healing length ξ H (T), and the dipolar length ξ D (T), which we report for pressures below 29 bar. A lattice of quantized vortex lines appears in the rotating state, and two additional textural free energy terms have to be included in the analysis. One of the terms is linear in the applied magnetic field and arises from the spontaneous magnetization of the vortex cores. The second term is quadratic in magnetic field; it is generated both by the superflow field v s (r) about the vortex core and the difference in the induced magnetizations of the vortex-core and the bulk superfluids. The rotational orienting effects have been studied for rotation speedsβ up to 2red/sec.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00681586
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  • 7
    Electronic Resource
    Electronic Resource
    Collective-mode spectroscopy of textures in superfluid3He-B (1989)
    Springer
    Journal of low temperature physics 77 (1989), S. 17-33 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A phenomenological theory for the propagation of the real squashing modes in superfluid3He-B is presented. This allows one to calculate the splitting of the real squashing (rsq) mode spectrum caused by the combined effects of magnetic field, dispersion, and texture in the experimentally important range of magnetic fields from 0 to 103 Gauss. This serves to provide a tool for the rsq-mode spectroscopy of the $$\hat n$$ -textures in3He-B. In particular, a new “gyrosonic effect” is suggested: the intensity of the rsq modes generated in textures depends on the sense of rotation—even when the axis of rotation $$\hat \Omega $$ coincides with the direction of the ultrasound propagation $$\hat q$$ .
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00681877
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  • 8
    Electronic Resource
    Electronic Resource
    Parameter-free quasiclassical boundary conditions for superfluid3He at rough walls. B-phase order parameter and density of states (1991)
    Springer
    Journal of low temperature physics 85 (1991), S. 267-282 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Parameter-free boundary conditions are discussed for the quasiclassical Green's functions at a rough wall. These conditions have a closed form: all information specific to the wall is eliminated under the assumption that the impurity layer covering the wall is much thicker than the mean-free path of quasiparticles. To demonstrate them in action we calculate the3He-B order parameter and the density of states, and compare them with previous work. Our main conclusion is that the new boundary conditions give qualitatively similar density of states as the “thin-impurity-layer” model, but different from that of the “randomly-rippled-wall” model. Moreover, our approach, being much simpler, allows us to resolve the fine structure of quasiparticle resonances which has not been reported earlier.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00681972
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  • 9
    Electronic Resource
    Electronic Resource
    Half-solitons in superfluid3He-A: Novel π/2-quanta of phase slippage (1989)
    Springer
    Journal of low temperature physics 74 (1989), S. 319-346 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Core structures of nontopological solitons between inequivalent vacua in superfluid3He-A are considered. We analyze the symmetries of these A-A interfaces, and compute their hard-core structures in the Ginzburg-Landau regime. We discuss both domain walls where the orbital anisotropy l-vector is flipped (l→−l), and those with the same l(x=−∞) and l(x=+∞) asymptotics. In particular, we find new classes of A-A boundaries: these novel π/2-solitons, which can occur in the absence of a change in the asymptotic l-vector field, constitute the elementary quanta of phase slippage in superfluid3He-A. We ascribe these “half-solitons” to a new topological scenario for the flaring-out of vorticity in the extended (k, r)-space. Edges of such walls serve to provide vortices with 1/4 quantum of circulation in3He-A. In analogy with the B-B domain walls in superfluid3He-B, solitons of pure phase slippage by π—with a normal core—prove unstable in3He-A; they either fission into a pair of ordinary l-solitons—domain walls with superfluid cores both flipping the orbital anisotropy axis (i.e., l→−l→l), or form a bound pair of walls, each of which constitutes an l-soliton with a phase shift of π/2. Our investigation of the superfluid A-A vacuum interfaces may prove useful in a broader context since the A-A boundaries exemplify the possible domain walls relevant for the Higgs-field solitons (“cosmic domain walls”) within the Weinberg-Salam model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00683378
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  • 10
    Electronic Resource
    Electronic Resource
    Fluctuations in small volumes of liquid 3He (1981)
    Springer
    Journal of low temperature physics 42 (1981), S. 35-46 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: We calculate fluctuation contributions to the thermodynamic properties in a small volume of liquid 3He. Functional integration techniques are employed to derive the fluctuation free-energy functional for temperatures just above the superfluid transition temperature and for zero temperature. Due to finite-size effects, the critical regime is estimated to be large enough to warrant an experimental observation of fluctuations. At zero temperature we find two kinds of quasicollective gapless excitations, which correspond to fluctuations of phase and rotations of the order parameter in spin space, respectively. These excitations result in a periodic time dependence of the pair correlation function. Finally, the experimental observability of the effects considered are contemplated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00116694
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