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We have investigated shot noise in a 6-nm-diameter, semiconducting multiwalled carbon nanotube field effect transistor at 4.2 K over the frequency range of 600-950 MHz. We find a transconductance of 3-3.5 μS for optimal positive ...
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We have investigated shot noise in a 6-nm-diameter, semiconducting multiwalled carbon nanotube field effect transistor at 4.2 K over the frequency range of 600-950 MHz. We find a transconductance of 3-3.5 μS for optimal positive and negative source-drain voltages V. For the gate referred input voltage noise, we obtain 0.2 and 0.3 μV/(Hz)~(1/2) for V > 0 and V < 0, respectively. As effective charge noise, this corresponds to (2-3) x 10~(-5)e/(Hz)~(1/2).
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Textures, textural transformation, and formation and annihilation of a single vortex were investigated in narrow cylinders with 100 μm radius in A-phase under rotation up to 6.28 rad/sec. Three textures were found, depending on t...
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Textures, textural transformation, and formation and annihilation of a single vortex were investigated in narrow cylinders with 100 μm radius in A-phase under rotation up to 6.28 rad/sec. Three textures were found, depending on the cooling conditions of the sample through the superfluid transition temperature T_c. We found the gyromagnetic effect of textures; that is, two textures (A or B) could be selected either by applying a magnetic field in parallel or anti-parallel to the rotation axis. The critical angular speed of a single vortex formation Ω_f and that of annihilation Ω_a for each texture were measured. The textural transformation in type A texture was induced by rotation. Both type A and B textures held macroscopic angular momentum along the rotation axis. We identified the texture for type A, B, and C as Mermin-Ho, radial disgyration, and a soliton type of defect along the axis, respectively.
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We experimentally corroborate the core analytical deductions of Thomson's 124-year-old theorem, visa-vis the stability of a ring of N vortices. Observations made in water vortices produced inside a cylinder via a revolving disk co...
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We experimentally corroborate the core analytical deductions of Thomson's 124-year-old theorem, visa-vis the stability of a ring of N vortices. Observations made in water vortices produced inside a cylinder via a revolving disk confirm that the regular N-
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Torsional oscillations, temporal variations in the differential rotation in rotating systems, are a well-established phenomenon in the fluid regions of convective stars and planets. We show for the first time that nonlinear torsio...
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Torsional oscillations, temporal variations in the differential rotation in rotating systems, are a well-established phenomenon in the fluid regions of convective stars and planets. We show for the first time that nonlinear torsional oscillations can be generated and maintained by convective instabilities in rotating systems.
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We present experimental, numerical, and theoretical studies oi' a vortex front propagating into a region of vortex-free flow of rotating superfluid ~3He-B. We show that the nature of the front changes from laminar through quasicla...
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We present experimental, numerical, and theoretical studies oi' a vortex front propagating into a region of vortex-free flow of rotating superfluid ~3He-B. We show that the nature of the front changes from laminar through quasiclassical turbulent to quantum turbulent with decreasing temperature. Our experiment provides the first direct measurement of the dissipation rate in turbulent vortex dynamics of ~3He-B and demonstrates that the dissipation becomes mutual-friction independent with decreasing temperature, and it is strongly suppressed when the Kelvin-wave cascade on vortex lines is predicted to be involved in the turbulent energy transfer to smaller length scales.
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We study a twisted vortex bundle where quantized vortices form helices circling around the axis of the bundle in a "force-free" configuration. Such a state is created by injecting vortices into a rotating vortex-free superfluid. U...
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We study a twisted vortex bundle where quantized vortices form helices circling around the axis of the bundle in a "force-free" configuration. Such a state is created by injecting vortices into a rotating vortex-free superfluid. Using continuum theory we determine the structure and the relaxation of the twisted state. This is confirmed by numerical calculations. We also present experimental evidence of the twisted vortex state in superfluid ~3He-B.
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A stretched vortex model is proposed which includes a nonuniform stretching in the radial direction that is clearly present in real flows, as well as a slow variation of velocity profiles along the vortex axis. Both features of th...
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A stretched vortex model is proposed which includes a nonuniform stretching in the radial direction that is clearly present in real flows, as well as a slow variation of velocity profiles along the vortex axis. Both features of this boundary layer approximation depart from the classical Burgers solution. This model is shown to be in very good agreement with experimental velocity measurements.
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We derive the equation governing the asymptotic stationary states generated by decaying turbulence in two-dimensional plasma and planetary atmosphere. These fluids may be described by the Charney-Hasegawa-Mima equation and their r...
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We derive the equation governing the asymptotic stationary states generated by decaying turbulence in two-dimensional plasma and planetary atmosphere. These fluids may be described by the Charney-Hasegawa-Mima equation and their relaxation states show a high degree of organization in vortical flows, similar to the Euler fluid. We develop a field-theoretical framework and show that these systems attain at stationarity the extremum of an energy functional corresponding to self-dual fields.
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Self-consistent finite-mode approximations for both Euler and Navier-Stokes equations for vorticity on a sphere are constructed and extended to the case of a rotating sphere, aiming at application to ocean and atmosphere modeling....
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Self-consistent finite-mode approximations for both Euler and Navier-Stokes equations for vorticity on a sphere are constructed and extended to the case of a rotating sphere, aiming at application to ocean and atmosphere modeling. In the absence of dissipation they preserve the specific Hamiltonian structure of hydrodynamics and have, at cach level of approximation, an appropriate number of integrals of motion, which is not the case for standard schemes.
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We investigate experimentally the deformation of acoustic wavefronts after crossing of a single, isolated vortex in free space. The incident sound wavelength can be varied in a large domain. We study the wavefronts at variable dis...
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We investigate experimentally the deformation of acoustic wavefronts after crossing of a single, isolated vortex in free space. The incident sound wavelength can be varied in a large domain. We study the wavefronts at variable distance after transmission through the vortex, when the wavelength and the vortex strength are varied. For small wavelength (λ <收起
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