Herbsommer, J. A., G. Nieva, and J. Luzuriaga. "Interplay between pinning energy and vortex interaction in YBa2Cu3O7-delta with oriented twin boundaries in tilted magnetic fields: Bitter decoration and tilt-modulus measurements." Physical Review B 62, no. 5 (2000): 3534–3541.
Abstract: We have performed Bitter decoration and ac susceptibility measurements in single-crystal YBa2Cu3O7-delta with oriented twin boundaries. The twin boundaries (TB's) pin vortices over approximately 65% of the sample. The pinned areas are unevenly distributed and some relatively large TB-free regions are present. The Bitter decorations were performed in a 52 Oe de magnetic field rotated off the c axis so that the plane defined by the field direction and the c axis is perpendicular to the TB's. Several decorations were performed in the same sample. Additional dynamical information was obtained from ac susceptibility measurements. Results show that for small tilts the vortices remain locked to the c-axis direction, for angles greater than 12 degrees they form a staircase pattern, and in this case pinning by the twin boundaries remains effective up to 75 degrees. We observe vortex chains in twin-free-zones of the sample for tilted fields at 65 degrees and 40 degrees. Due to our particular experimental arrangement, in the twinned regions the interplay of the potentials giving rise to the chains and the pinning potential produces a structure with a disordered square symmetry. The data allow us to estimate the dominant energy of the vortex system for some inclinations of the applied magnetic field.
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Herbsommer, J. A., G. Nieva, and J. Luzuriaga. "Repetition of the disordered pattern in successive solidifications of vortex matter observed by Bitter decoration." Physical Review B 62, no. 1 (2000): 678–681.
Abstract: Repeated images of the vortex structure in YBa2Cu3O7-delta Single crystals have been obtained, using the Bitter technique. By removing the iron dots between each decoration experiment, it is possible to image the vortices in different cooldown runs done under the same field and temperature conditions. The images show that these different realizations of a disordered vortex state found in twinned crystals are very similar at long range and differ only in small-scale detail. This is unusual behavior in glassy systems, where expectations are that successive configurations will differ over many scales. In contrast, ordered vortex crystals in clean samples can form with different orientations in different runs, therefore differing at long ranges. Double-sided decorations have been performed in twinned samples, and the correlation between images in both sides of the sample is similar in magnitude but slightly different qualitatively than that found in successive decorations.
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Herbsommer, J. A., G. Nieva, and J. Luzuriaga. "Interaction of vortices with oriented twin boundaries in single-crystal YBa2Cu3O7-delta." Physical Review B 61, no. 17 (2000): 11745–11751.
Abstract: We have studied the response of the vortex lattice (VL) in a YBa2Cu3O7-delta sample with oriented twin boundaries (TB's) and in an untwinned sample. In the twinned sample the density of twin boundaries is estimated from decoration experiments. The TB's affect the liquid-to-solid transition in the vortex structure, which is of first order in the twin free crystal and to a Bose glass in the twinned sample. We measure the ac susceptibility, and find that the response strongly depends on the orientation of the probing ac field with respect to the TB's. The ac field produces a tilting stress on the vortices. With the applied de magnetic field H-dc parallel to the c axis, the response of the VL is weaker when the tilt is parallel to the TB's than when it is perpendicular or at 45 degrees to the TB's. The results are explained by the fact that the VL is locked to the twin boundaries for small deviations of H-dc from the c axis and is partially pinned to them for larger angles. By measuring over the whole angular range we estimate the angles over which each regime is realized for different temperatures. The results of the detwinned sample are used for comparison.
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Konstantinov, D., W. Homsi, J. Luzuriaga, C. - K. Su, M. A. Weilert, and H. J. Maris. "How Does a Bubble Chamber Work?" Journal of Low Temperature Physics 113, no. 3-4 (1998): 485–490.
Abstract: A charged particle passing through a bubble chamber produces a track of bubbles. The way in which these bubbles are produced has been a matter of some controversy. We consider the possibility that in helium and hydrogen bubble chambers the production of bubbles is primarily a mechanical process, rather than a thermal process as has often been assumed. The model we propose gives results which are in excellent agreement with experiment.
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Luzuriaga, J. "Mean free path in soccer and gases." European Journal of Physics 31, no. 5 (2010): 1071–1076.
Abstract: The trajectories of the molecules in an ideal gas and of the ball in a soccer game are compared. The great difference between these motions and some similarities are discussed. This example could be suitable for discussing many concepts in kinetic theory in a way that can be pictured by students for getting a more intuitive understanding. It could be suitable for an introductory course in vacuum techniques or undergraduate courses in kinetic theory of gases. Without going into the slightly harder quantitative results, the analysis presented might be used for introducing some ideas of kinetic theory qualitatively to high school students. © 2010 IOP Publishing Ltd.
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Luzuriaga, J. "Even in translation, Richter's 'science' unimpressive." Physics Today 58, no. 1 (2005): 14–15.
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Luzuriaga, J. "Comment on “Super classical quantum mechanics: The best interpretation of nonrelativistic quantum mechanics”." American Journal of Physics 70, no. 1 (2002): 10.
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Luzuriaga, J. "Sphere on a vibrating reed for measurements of turbulence in superfluid helium." Journal of Alloys and Compounds (2000): 265–268.
Abstract: A modification of the vibrating reed, in which a massive sphere is made to oscillate at the end of a cantilevered beam, has been used for measurements in superfluid helium. The apparatus operates in the same way as a conventional vibrating reed with capacitive detection and drive. However, when operating submerged in the liquid, the frequency changes give information on the superfluid fraction, and the dissipation can be used to obtain information on the change of liquid flow, from laminar to turbulent. The spherical geometry allows an exact calculation of all parameters in the laminar regime, so departures due to the turbulence can be better quantified. The method has been found to work well in practice, and some measurements on the turbulent regime in the superfluid are presented.
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Luzuriaga, J. "Measurements in the laminar and turbulent regime of superfluid4He by means of an oscillating sphere." Journal of Low Temperature Physics 108, no. 3-4 (1997): 267–277.
Abstract: The translational oscillations of a sphere in liquid helium have been measured as a way of studying superfluid turbulence. Experiments were carried out in the laminar flow regime for reference purposes, and good agreement found between measured and calculated quantities. In the turbulent region, the dissipation is found to be proportional to the square of the velocity of the sphere, as found previously by other workers. For high vibration amplitudes there is an increase in the hydrodynamic mass. This seems to scale with the superfluid fraction in a way that strongly suggests that the superfluid component plays an important role in the turbulent regime.
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Luzuriaga, J. "Upper critical field in superconductors and the uncertainty principle: Upper limit to the maximum slope of Hc2." Physical Review B 42, no. 1 (1990): 934–935.
Abstract: Consideration of the formulas that give the upper critical field Hc2 near the critical temperature Tc for superconductors in the dirty limit, together with the uncertainty principle, is shown to provide an upper limit to the maximum slope of Hc2. Analysis of reported values shows that amorphous superconductors are in this limit.
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