Luzuriaga, J., M. - O. Andre, and W. Benoit. "Frequency and amplitude response of the flux-line lattice to mechanical perturbation in ceramic YBa2Cu3O7." Physica C: Superconductivity and its applications 201, no. 3-4 (1992): 257–262.
Abstract: The mechanical response of the flux-line lattice has been measured with a low-frequency forced pendulum in ceramic YBa2Cu3O7. A dissipation peak observed in temperature sweeps is frequency-independent between 1 mHz and 5 Hz. Dissipation depends strongly on applied torque, and for fixed temperatures this dependence is well fitted by a rheological model of extended dry friction. If the model is extended to take account of thermal activation, however, it does not agree with the measured frequency independence, which is hard to explain within simple models of thermal activation.
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Rodr. "Role of anisotropy in the vortex lattice of superconductors high-Q oscillator measurements in 2H-NbSe2 and La1.825Sr0.075CuO4." Physica C: Superconductivity and its applications 229, no. 1-2 (1994): 59–64.
Abstract: Measurement of the response of the flux-line lattice in NbSe2 and La1.825Sr0.075CuO4 show important differences between these two materials. In particular, we have studied the magnetic-field and angular dependence of the response of a high-Q mechanical oscillator in fields of up to 1 T. The features seen in NbSe2 seem to be well explained in terms of a change in the pinning regime, usually termed the “peak effect” in the critical current, using the collective-pinning model of Larkin and Ovchivnikov within Ginzburg-Landau anisotropic theory. On the other hand the behavior found in the high-Tc material LSCO seems to fall naturally into a description which takes into account the possibility of phase transitions in the vortex lattice and the quasi-two-dimensional character of the superconductivity.
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D'Anna, G., and Andr. "Flux-line response in 2H-NbSe2 investigated by means of the vibrating superconductor method." Physica C: Superconductivity and its applications 218, no. 1-2 (1993): 238–244.
Abstract: We measure transverse AC losses in the low- and high-amplitude regime of 2H-NbSe2 single crystals using vibrating superconductor methods. The measurements are sensitive to small deviations of the critical state. The data constitute evidence for a peak effect of the critical current as a function of the temperature in this compound. We construct in the H-T phase diagram the “peak-effect” line which is supposed to mark an abrupt cross-over in the vortex-pinning regime.
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Haberkorn, N., S. Suárez, P. D. Pérez, H. Troiani, P. Granell, F. Golmar, J. - H. Lee, and S. H. Moon. "Effect of mixed pinning landscapes produced by 6 MeV oxygen irradiation on the resulting critical current densities Jc in 1.3 µm thick GdBa2Cu3O7-d coated conductors grown by co-evaporation." Physica C: Superconductivity and its Applications 542 (2017): 6–11.
Abstract: We report the influence of crystalline defects introduced by 6 MeV 16O3+ irradiation on the critical current densities Jc and flux creep rates in 1.3 µm thick GdBa2Cu3O7-δ coated conductor produced by co-evaporation. Pristine films with pinning produced mainly by random nanoparticles with diameter close to 50 nm were irradiated with doses between 2 × 1013 cm−2 and 4 × 1014 cm−2. The irradiations were performed with the ion beam perpendicular to the surface of the samples. The Jc and the flux creep rates were analyzed for two magnetic field configurations: magnetic field applied parallel (H║c) and at 45° (H║45°) to the c-axis. The results show that at temperatures below 40 K the in-field Jc dependences can be significantly improved by irradiation. For doses of 1 × 1014 cm−2 the Jc values at μ0H = 5 T are doubled without affecting significantly the Jc at small fields. Analyzing the flux creep rates as function of the temperature in both magnetic field configurations, it can be observed that the irradiation suppresses the peak associated with double-kink relaxation and increases the flux creep rates at intermediate and high temperatures. Under 0.5 T, the flux relaxation for H‖c and H||45° in pristine films presents characteristic glassy exponents μ = 1.63 and μ = 1.45, respectively. For samples irradiated with 1 × 1014 cm−2, these values drop to μ = 1.45 and μ = 1.24, respectively
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Lee, S. - C., M. Sullivan, G. R. Ruchti, S. M. Anlage, B. S. Palmer, B. Maiorov, and E. Osquiguil. "Doping-dependent nonlinear Meissner effect and spontaneous currents in high-Tc superconductors." Physical Review B – Condensed Matter and Materials Physics 71, no. 1 (2005).
Abstract: We measure the local harmonic generation from superconducting thin films at microwave frequencies to investigate the intrinsic nonlinear Meissner effect near Tc in the zero magnetic field. Both second and third harmonic generation are measured to identify time-reversal symmetry breaking (TRSB) and time-reversal symmetric (TRS) nonlinearities. We perform a systematic doping-dependent study of the nonlinear response and find that the TRS characteristic nonlinearity current density scale follows the doping dependence of the depairing critical current density. We also extract a spontaneous TRSB characteristic current density scale that onsets at Tc, grows with decreasing temperature, and systematically decreases in magnitude (at fixed T/TC) with underdoping. The origin of this current scale could be Josephson circulating currents or the spontaneous magnetization associated with a TRSB order parameter.
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Maiorov, B., and E. Osquiguil. "Vortex solid state in YBa2Cu3O7-? twinned crystals." Physical Review B – Condensed Matter and Materials Physics 64, no. 5 (2001): 0525111–0525114.
Abstract: We report on the scaling of transport properties around the vortex melting in YBa2Cu3O7-? oriented-twin single crystals in applied magnetic fields between 1 T and 18 T. We find that for the whole measured field range the linear resistivity scales as ?(t,?)?tsyF
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Rigal, L. B., D. C. Schmadel, H. D. Drew, B. Maiorov, E. Osquiguil, J. S. Preston, R. Hughes, and G. D. Gu. "Magneto-optical evidence for a gapped Fermi surface in underdoped YBa 2Cu3O6+x." Physical Review Letters 93, no. 13 (2004).
Abstract: An evidence presented that supports partial gapping of the Fermi surface by a measurement of the Hall frequency from high frequency magneto-optical measurements on underdoped YBa2Cu3O6+x (YBCO) was discussed. It was found that the Hall frequency was obtained independently of the unknown k-space dependence of the carrier scattering rates that complicated the dc Hall effect. It was observed that the frequency dependence of the Hall angle was Drude-like and indicated a quasielastic relaxation process for optimal and underdoped samples. The results show that there was an increase of the Hall frequency in the pseudogap state.
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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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Martínez, E. D., A. F. García Flores, H. Pastoriza, R. R. Urbano, and C. Rettori. "Electrothermal Silver Nanowire Thin Films for In-Situ Observation of Thermally-Driven Chemical Processes." Sensors and Actuators B: Chemical 259 (2017): 475–483.
Abstract: We develop a novel device comprised of high optical transmittance thin films containing silver nanowires (AgNWs) in poly(methyl methacrylate) (PMMA) acting as heating elements. The electrothermal control of the AgNWs network allows us to externally trigger and tune the temperature conditions required to run chemical reactions and physicochemical processes. The device was successfully applied for the spectroscopic in-situ observation of three different model reactions: i) the thermal equilibrium of a CoCl2/HCl/H2O complex, ii) the reversible macromolecular phase transition of a pNIPAM solution, and iii) the nucleation and growth of gold nanoparticles (AuNPs). In the first case, the color of the Co2+ complex was reversibly switched from pink to blue when changing the thermal equilibrium condition. In the second one, the optical transmittance of an aqueous solution of carboxylic-terminated pNIPAM polymer was cycled from high to low as the temperature of the solution was below or above the lower critical solubility temperature (LCST) respectively. Finally, the electrothermal control on the device was applied to the study of the nucleation and growth of AuNPs in an organic solution of AuCl3 containing oleylamine acting as both the reducer and the stabilizing agent. The versatility of the electrothermal device provides an easy way to undertake thermally controlled processes and develop optical elements such as smart windows and lab-on-a-chip devices. The AgNWs-PMMA nanocomposite was also applied successfully as an electrothermal ink on the external side walls of a test tube.
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Rodriguez, E., J. Luzuriaga, M. Núñez Regueiro, and C. Fainstein. "Low temperature internal friction peak in high Tc superconductors." Solid State Communications 77, no. 10 (1991): 777–780.
Abstract: We measure the internal friction Q-1 in YBa2Cu3O7-x and Bi2Sr2CaCu2O8+x samples. At temperatures near 35 K for KHz frequencies we observe an attenuation peak. In the case of YBa2Cu3O7-x, assuming a thermally activated relaxation behaviour, we are able to show that it corresponds to the same process as other peaks observed at higher frequencies. For Bi2Sr2CaCu2O8+x this is not the case, and the origin of the peak, found in all the measured samples, remains unknown.
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