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Author Cruz, F. de la; Fasano, Y.; Seta, M.D.; Menghini, M.; Pastoriza, H.
Title Plastic and Elastic Symmetry Transformations Induced in the Vortex Lattice of Anisotropic and Layered Superconductors Type Journal Article
Year 2004 Publication Journal of Low Temperature Physics Abbreviated Journal
Volume 135 Issue Pages 99-110
Keywords
Abstract We make a comparative analysis of the response of the three-dimensional vortex lattice in Bi$2$Sr$2$CaCu$8$ and NbSe$2$ to the presence of square arrays of pinning sites localized at one extremity of the vortex crystals. The absence of the hexagonal to square symmetry transformation and the induction of a distorted hexagonal symmetry in the vortex lattice of NbSe$2$ contrast to the observed symmetry change in Bi$2$Sr$2$CaCu$8$. The dissimilar response in both cases is explained taking into account the vortex structure solidification mechanisms in both materials: The plastic response in the case of the layered material Bi$2$Sr$2$CaCu$8$ is suggested to be a result of the simultaneity of solidification and coupling of bidimensional pancake vortices whereas a viscous solidification is the responsible for the three-dimensional elastic response in NbSe$_2$.
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Call Number BT @ hernan @ delacruz04 Serial 15
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Author Hernandez,A.; Ares,O.; Hart, C.; Domínguez,D.; Pastoriza,H.; Butera, A.
Title Dissipation in mesoscopic superconductors with ac magnetic fields Type Journal Article
Year 2004 Publication Journal of Low Temperature Physics Abbreviated Journal
Volume 135 Issue Pages 119-122
Keywords
Abstract The response of mesoscopic superconductors to an ac magnetic field is investigated both experimentally

and with numerical simulations. We study small square samples with dimensions of the order of the penetration depth.

We obtain the ac susceptibitity $\chi=\chi'+\chi“$ at microwave frequencies as a function of the dc magnetic field

$H{dc}$. We find that the dissipation, given by $\chi”$, has a non monotonous behavior in mesoscopic samples.

In the numerical simulations we obtain that the dissipation increases before the penetration of vortices and

then it decreases abruptly after vortices have entered, the sample. This is verified experimentally, where we

find that $\chi"$ has strong oscillations as a function of $H
{dc}$ in small squares of Pb
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Call Number BT @ hernan @ hernandez04 Serial 24
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Author Marconi V. I.; Pastoriza, H.; Domínguez, D.
Title Transverse voltage in disordered Josephson junction arrays with diagonal bias Type Journal Article
Year 2004 Publication Journal of Low Temperature Physics Abbreviated Journal
Volume 135 Issue Pages 135-138
Keywords
Abstract We study numerically the effect of disorder in the transport properties of square Josephson junction arrays with a dc current applied in the diagonal direction ([11] direction). We obtain a finite transverse voltage in this case when we consider the presence of disorder in the critical currents of the junctions. We show that this behavior is in good agreement with previous experimental, results in square arrays with a diagonal current drive.
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Call Number BT @ hernan @ marconi04 Serial 27
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Author Shalóm, D. E.; Pastoriza, H.
Title Experimental Method to Measure Anisotropic Transport in 2D Superconductors Type Journal Article
Year 2004 Publication Journal of Low Temperature Physics Abbreviated Journal
Volume 135 Issue Pages 153-156
Keywords
Abstract A two-coil kinetic inductance technique for measuring anisotropic response in two-dimensional (2D) superconductors is presented. Serpentine-shaped coils are lithographically patterned directly on top of the sample, separated by isolation layers. The drive and receive coils are positioned in a way that enhances signal from longitudinal currents and reduces transversal ones, maximizing the ratio. Anisotropic transport can be directly measured with this technique, even when anisotropy is induced by the transport current.
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Call Number BT @ hernan @ shalom04a Serial 43
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Author Schmoranzer, D., Jackson,M., Zemma, E., Luzuriaga,J.
Title Double-Paddle Oscillators as Probes of Quantum Turbulence in the Zero Temperature Limit Type Journal Article
Year 2016 Publication Journal of Low Temperature Physics Abbreviated Journal
Volume 185 Issue Pages
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Call Number BT @ pedrazp @ Serial 745
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Author Zemma, E.; Tsubota, M.; Luzuriaga, J.
Title Possible visualization of a superfluid vortex loop attached to an oscillating Beam Type Journal Article
Year 2015 Publication Journal of Low Temperature Physics Abbreviated Journal J. Low Temp. Phys.
Volume 179 Issue 5 Pages 310-319
Keywords Quantum fluids; Superfluid helium; Flow visualization; Vortex loops
Abstract Visualization using tracer particles is a relatively new tool available for the study of superfluid turbulence and flow, which is applied here to oscillating objects submerged in the liquid. We report observations of a structure seen in videos taken from outside a cryostat filled with superfluid helium at 2 K, which is possibly a vortex loop attached to an oscillator. The feature, which has the shape of an incomplete arch, is visualized due to the presence of solid H2 tracer particles and is attached to a beam oscillating at 38 Hz in the liquid. It has been recorded in videos taken at 240 frames per second, fast enough to take ∼6 images per period. This makes it possible to follow the structure, and to see that it is not rigid. It moves with respect to the oscillator, and its displacement is in phase with the velocity of the moving beam. Analyzing the motion, we come to the conclusion that we may be observing a superfluid vortex attached to the beam and decorated by the hydrogen particles. An alternative model, considering a solid hydrogen filament, has also been analyzed, but the observed phase between the movement of the beam and the filamentary structure is better explained by the superfluid vortex hypothesis.
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Call Number BT @ pedrazp @ Serial 734
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Author Zemma, E.; Luzuriaga, J.
Title Measurements of Turbulence Onset and Dissipation in Superfluid Helium with a Silicon Double Paddle Oscillator Type Journal Article
Year 2012 Publication Journal of Low Temperature Physics Abbreviated Journal J. Low Temp. Phys.
Volume 166 Issue 3-4 Pages 171-181
Keywords
Abstract We have studied experimentally the response of a silicon single crystal double paddle oscillator submerged in superfluid helium from the lambda point to 1.55 K. Measuring the resonance frequency and dissipation on three modes of this high Q system allows us to study the dissipation at the onset of turbulence in the flow around the paddle. The critical velocity V c for turbulence onset decreases with temperature. If we use the density of the normal component of the superfluid to obtain a Reynolds number Re associated with V c we find a value which is largely temperature independent. This result is different from the behavior previously found by other authors below 1 K, where the quantized vorticity (extrinsic nucleation) is observed at velocities more than an order of magnitude greater. In our temperature range, we conclude that the transition is governed by the normal fraction acting as a classical fluid. The laminar regime shows a dissipation that is proportional to the viscous drag calculated by well known formulas for an object oscillating in a liquid. We also find a decrease in resonance frequency in the turbulent regime which is clearly observed but hard to reproduce from run to run.
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ISSN 1573-7357 ISBN Medium
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Notes (up) Approved no
Call Number BT @ hernan @ Serial 648
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Author Zemma, E.; Luzuriaga, J.
Title Anomalous Trajectories of H2 Solid Particles Observed Near a Sphere Oscillating in Superfluid Turbulent 4He Type Journal Article
Year 2013 Publication Journal of Low Temperature Physics Abbreviated Journal J. Low Temp. Phys.
Volume 173 Issue 1-2 Pages 71-79
Keywords Quantum fluids; Turbulence; Superfluid helium; Flow visualization; Oscillating sphere
Abstract Using a relatively low cost apparatus, consisting of a glass dewar and a digital camera capable of taking images at 240 frames per second we have observed trajectories of frozen H2 particles which follow the flow of liquid helium below 2 K, around a sphere oscillating at 38 Hz. In some of the images the motion is compatible with laminar flow, while at high amplitudes, where we can reach Reynolds numbers of a few thousand in the normal component, the flow is clearly turbulent. In some of the videos taken we find particles being suddenly accelerated to several times the velocity of the oscillating sphere.
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Publisher Springer US Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0022-2291 ISBN Medium
Area Expedition Conference
Notes (up) Approved no
Call Number BT @ pedrazp @ Serial 661
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Author Zemma, E.; Luzuriaga, J.
Title Turbulent Flow Around an Oscillating Body in Superfluid Helium: Dissipation Characteristics of the Nonlinear Regime Type Journal Article
Year 2013 Publication Journal of Low Temperature Physics Abbreviated Journal J. Low Temp. Phys.
Volume 172 Issue 3-4 Pages 256-265
Keywords Quantum fluids; Turbulence; Superfluid helium; Nonlinear oscillator; Vibrating paddle; Critical velocity
Abstract By examining the resonance curves of an oscillator submerged in superfluid liquid helium, it is found that their shape is affected by two distinct dissipation regimes when the amplitude is large enough to generate turbulence in the liquid. In a resonance curve, the central part close to resonance, may be in a turbulent regime, but the response is of much lower amplitude away from the resonance frequency, so that the oscillation can still be in the linear regime for frequencies not exactly at resonance. This introduces an ambiguity in estimating the inverse quality factor Q −1 of the oscillator. By analyzing experimental data we consider a way of matching the two ways of estimating Q −1 and use the information to evaluate the frictional force as a function of velocity in a silicon paddle oscillator generating turbulence in the superfluid.
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Corporate Author Thesis
Publisher Springer US Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0022-2291 ISBN Medium
Area Expedition Conference
Notes (up) Approved no
Call Number BT @ pedrazp @ Serial 662
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Author Schmoranzer, D.; Jackson, M.J.; Luzuriaga, J.
Title On the Non-linear Damping of Mechanical Oscillators in Flows of 4He Type Journal Article
Year 2014 Publication Journal of Low Temperature Physics Abbreviated Journal J. Low Temp. Phys.
Volume 175 Issue 1 Pages 97-103
Keywords Resonator; Non-linear dissipation; Turbulence; Liquid helium
Abstract In the studies of both classical and quantum turbulence, significant attention is devoted to the investigation of the behavior of various submerged resonators. Upon entering the turbulent regime, the oscillators start to experience a significant drag force, which varies non-linearly with velocity. We present an empirical way of modeling such systems, and calculate the expected resonant response of such oscillators near the fundamental frequency as a function of the applied driving force. We apply the model to the crossover from linear to non-linear drag forces and compare with previous models as well as selected experimental data on the transition to turbulence in oscillatory flow of 4He.
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Corporate Author Thesis
Publisher Springer US Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0022-2291 ISBN Medium
Area Expedition Conference
Notes (up) Approved no
Call Number BT @ pedrazp @ Serial 663
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