1,354,369 research outputs found
Magnetic field dependence of the voltage output of Josephson junctions current-biased on Fiske steps
No full text
Zero bias conductance peaks in high-T-c superconductors: clues and ambiguities of two mutually excluding models
No full textThe origin of the zero bias conductance peak (ZBCP) observed in the tunneling characteristics of different high-T-c based junctions, is analyzed in the framework of the Anderson-Applebaum theory for Kondo type scattering from magnetic impurities at the barrier or in terms of midgap states induced by proximity effect at the surface of a d(x2-y2) wave superconductor. The two models mutually exclude each other since they describe a normal state or a superconducting state effect, respectively. We show that the appearance of the anomaly above or below the junction T-c, is the main indication that enable us to distinguish between the two cases. In addition to this, in the most controversial situations, the simultaneous presence at low temperatures of dips on both sides of the central structure as well as of conductance maxima at the expected values of the main high-T-c superconductor(HTS) energy gap, can be considered as indications of d-wave superconductivity. The case of ZBCP's that for decreasing temperatures merge in conductance minima, is also discussed
Microwave intermodulation study of YBa2Cu3O7-x films in the presence of an external d.c. magnetic field
No full textRole of Cooper Inter-electron interaction with pseudogaps opening in HTS tunneling experiments
No full textUltrathin superconducting Yba2Cu3O7-δ films obtained by high oxygen pressure DC sputterind technique
No full textMetal-insulator transition temperature enhancement in La0.7Ca0.3MnO3 thin films
No full textThe effect of oxygen annealing on the structural and transport properties of La0.7Ca0.3MnO3 thin films deposited on SrTiO3 substrates has been investigated by x-ray diffraction analysis and resistive measurements. The as-grown films are fully tensile strained on the substrates and show a depressed metal-insulator transition temperature T-p= 131 K. As the oxygen content is increased due to longer annealing times, significantly higher T-p are measured, up to 247 K. Correspondingly, an increase of the out-of-plane lattice parameter is observed while the in-plane lattice constants do not change with respect to the as-grown films, which prevents any interpretation of a T-p dependence on the strain. The large increase in T-p is then interpreted in terms of a combined effect of the Mn4+/Mn3+ ratio variation, the change in the carrier density in the a-b planes, and the increase in the hydrostatic strain with the oxygen annealing
Thermodynamics of second order phase transition in a molecular field theory for inhomogeneous systems proximity sandwiches
No full textNous prouvons par la méthode de la théorie des bifurcations que dans les systèmes inhomogènes décrits par la théorie du champ moléculaire de Landau il y a une transition de phase du deuxième ordre. En particulier nous vérifions les conditions thermodynamiques de Ehrenfest dans le cas d'un sandwich normal-superconducteur-normal où est présent l'effet de proximité décrit par l'équation de de Ginzburg-Landau (ou par les équations G-L généralisées) et par la fonction de l'énergie libre correspondante en l'absence de champ magnétique extérieur.Using bifurcation theory we prove that second order phase transitions occur in inhomogeneous systems described by the molecular Landau field theory. In particular the Ehrenfest thermodynamic conditions are satisfied by normal-superconducting-normal proximity effect sandwiches described by the Ginzburg-Landau equations (or the extended G-L equations) and by the corresponding free energy function in the absence of external magnetic fields
Ordering of the Vortex Lattice in MoRe Films
No full textWe investigated the vortex lattice ordering induced by an applied
current in thick (700–900 nm) Mo-Re films with strong
pinning. Measurements of I-V characteristics as a function of
field and at different temperatures were carried out. We found
that, as in the case of weakly pinning amorphous samples, dynamic
ordering can occur only if the size of the vortex correlated
region is at least two times the intervortex distance
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