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Abraham, J., P. Abreu, M. Aglietta, C. Aguirre, D. Allard, I. Allekotte, J. Allen, P. Allison, J. Alvarez-Muniz, M. Ambrosio et al. "Observation of the suppression of the flux of cosmic rays above 4x10(19) eV." PHYSICAL REVIEW LETTERS 101, no. 6 (2008).
Abstract: The energy spectrum of cosmic rays above 2.5 x 10(18) eV, derived from 20 000 events recorded at the Pierre Auger Observatory, is described. The spectral index gamma of the particle flux, J proportional to E-gamma, at energies between 4 x 10(18) eV and 4 x 10(19) eV is 2.69 +/- 0.02(stat) +/- 0.06(syst), steepening to 4.2 +/- 0.4(stat) +/- 0: 06 (syst) at higher energies. The hypothesis of a single power law is rejected with a significance greater than 6 standard deviations. The data are consistent with the prediction by Greisen and by Zatsepin and Kuz'min.
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Abraham, J., P. Abreu, M. Aglietta, C. Aguirre, D. Allard, I. Allekotte, J. Allen, P. Allison, J. Alvarez-Muniz, M. Ambrosio et al. "Upper limit on the diffuse flux of ultrahigh energy tau neutrinos from the Pierre Auger Observatory." PHYSICAL REVIEW LETTERS 100, no. 21 (2008).
Abstract: The surface detector array of the Pierre Auger Observatory is sensitive to Earth-skimming tau neutrinos that interact in Earth's crust. Tau leptons from nu(tau) charged-current interactions can emerge and decay in the atmosphere to produce a nearly horizontal shower with a significant electromagnetic component. The data collected between 1 January 2004 and 31 August 2007 are used to place an upper limit on the diffuse flux of nu(tau) at EeV energies. Assuming an E-nu(-2) differential energy spectrum the limit set at 90% C. L. is E(nu)(2)dN(nu tau)/dE(nu) < 1: 3 x 10(-7) GeV cm(-2) s(-1) sr(-1) in the energy range 2 x 10(17) eV< E-nu < 2 x 10(19) eV.
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Bridoux, G., G. Nieva, and F. de la Cruz. "Phase-coherence effects in vortex transport entropy." PHYSICAL REVIEW LETTERS 101, no. 11 (2008): 117002.
Abstract: Nernst and electrical resistivity measurements in superconducting YBa2Cu3O7-delta and Bi2Sr2CaCu2O8+delta with and without columnar defects show a distinctive thermodynamics of the respective liquid vortex matter. At a field-dependent high temperature region in the H-T phase diagram, the Nernst signal is independent of structural defects in both materials. At lower temperatures, in YBa2Cu3O7-delta, defects contribute only to the vortex mobility, and the transport entropy is that of a system of vortex lines. The transition to lower temperatures in Bi2Sr2CaCu2O8+delta has a different origin; the maximum in the Nernst signal when decreasing temperature is not associated with transport properties but with the entropy behavior of pancake vortices in the presence of structural defects.
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Correa, V. F., S. Francoual, M. Jaime, N. Harrison, T. P. Murphy, E. C. Palm, S. W. Tozer, A. H. Lacerda, P. A. Sharma, and J. A. Mydosh. "High magnetic field lattice length changes in URu2Si2." Physical Review Letters 109 (2012): 246405.
Abstract: We report high-magnetic-field (up to 45 T) ^ c-axis thermal-expansion and magnetostriction experiments on URu2Si2 single crystals. The sample length change associated with the transition to the ‘‘hidden order’’ phase becomes increasingly discontinuous as the magnetic field is raised above 25 T. The
reentrant ordered phase III is clearly observed in both the thermal expansion and magnetostriction above 36 T, in good agreement with previous results. The sample length is also discontinuous at the boundaries of this phase, mainly at the upper boundary. A change in the sign of the coefficient of thermal expansion is observed at the metamagnetic transition (BM 38 T), which is likely related to the existence of a quantum critical end point.
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Correa, V. F., G. Nieva, and F. de la Cruz. "Vortex softening: Origin of the second peak effect in Bi2Sr2CaCu2O8+delta." PHYSICAL REVIEW LETTERS 87, no. 5 (2001): 057003.
Abstract: Magnetic hysteresis and transverse ac permeability measurements in Bi2Sr2CaCu2O8+delta allow a comparative analysis of the critical current with the elastic response of vortex structures, in equilibrium with their pinning potential, in the field and temperature region where the second peak is detected. This study provides strong evidence that the second peak has its origin in changes of the elastic equilibrium properties of the vortex structures.
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Decca, R. S., H. D. Drew, E. Osquiguil, B. Maiorov, and J. Guimpel. "Anomalous proximity effect in underdoped YBa2Cu3O6+x Josephson junctions." Physical Review Letters 85, no. 17 (2000): 3708–3711.
Abstract: Experiments were carried out to probe the underdoped insulating material by the Josephson effect. Junctions were fabricated by exploiting the capability of locally photodoping insulating RBa2Cu3O6+x (R = rare earth) material. The existence of an anomalously large proximity effect was confirmed. The critical current of the junctions was consisted with the conventional Josephson relationship.
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Dolz, M I., Y. Fasano, N R. Cejas Bolecek, H. Pastoriza, V. Mosser, M. Li, and M. Konczykowski. "Size-Induced Depression of First-Order Transition Lines and Entropy Jump in Extremely Layered Nanocrystalline Vortex Matter." Physical Review Letters 115, no. 13 (2015): 137003.
Abstract: We detect the persistence of the solidification and order-disorder first-order transition lines in the phase diagram of nanocrystalline Bi2Sr2CaCu2O8 vortex matter down to a system size of less than one hundred vortices. The temperature location of the vortex solidification transition line is not altered by decreasing the sample size although there is a depletion of the entropy jump at the transition with respect to macroscopic vortex matter. The solid order-disorder phase transition field moves upward on decreasing the system size due to the increase of the surface-to-volume ratio of vortices entailing a decrease on the average vortex binding energy.
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Fasano, Y., I. Maggio-Aprile, N. D. Zhigadlo, S. Katrych, J. Karpinski, and Ã. ˜. Fischer. "Local quasiparticle density of states of superconducting SmFeAsO1 − xFx single crystals: Evidence for spin-mediated pairing." Physical Review Letters 105 (2010): 167005–167008.
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Fullerton, E. E., J. Guimpel, O. Nakamura, and I. K. Schuller. "Structure of high-T_{c} superlattices." Physical Review Letters 69, no. 19 (1992): 2859.
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Fullerton, E. E., D. M. Kelly, J. Guimpel, I. K. Schuller, and Y. Bruynseraede. "Roughness and giant magnetoresistance in Fe/Cr superlattices." Physical Review Letters 68, no. 6 (1992): 859.
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