G. Leibovitch

Andreev reflections on Y(1-x)Ca(x)Ba(2)Cu(3)O(7-delta): evidence for an unusual proximity effect.

We have measured Andreev reflections between an Au tip and Y(1-x)Ca(x)Ba(2)Cu(3)O(7-delta) thin films in the in-plane orientation. The conductance spectra are best fitted with a pair potential having the d(x2-y2)+is symmetry. We find that the amplitude of the is component is enhanced as the contact transparency is increased. This is an indication for an unusual proximity effect that modifies the pair potential in the superconductor near the surface with the normal metal.

Transition from a mixed to a pure d-wave symmetry in superconducting optimally doped YBa2Cu3O7-x thin films under applied fields.

We have probed the Landau levels of nodal quasiparticles by tunneling along a nodal direction of (110) oriented YBa2Cu3O7-x thin films with a magnetic field applied perpendicular to the CuO2 planes, and parallel to the films surface. In optimally doped films and at low temperature, finite energy nodal states are clearly observed in films thinner than the London penetration depth. Above a well defined temperature, the order parameter reverts to a pure d-wave symmetry.

Transition in the tunneling conductance of YBa2Cu3O7-δ films in magnetic fields up to 32.4 T

We studied the tunneling density of states in YBCO films under strong currents flowing along node directions. The currents were induced by fields of up to 32.4T parallel to the film surface and perpendicular to the

Local tunneling probe of (110) Y0.95 Ca0.05 Ba 2Cu3 O7-δ thin films in a magnetic field

CuO_{2}

Field-induced nodal order parameter in the tunneling spectrum of Y Ba 2 Cu 3 O 7 − x superconductor

planes. We observed a remarkable change in the tunneling conductance at high fields where the gap-like feature shifts discontinuously from 15meV to a lower bias of 11meV, becoming more pronounced as the field increases. The effect takes place in increasing fields around 9T and the transition back to the initial state occurs around 5T in decreasing fields. We argue that this transition is driven by surface currents induced by the applied magnetic field.

High Quality a-axis outgrowth on c-axis YlCa1-xBa2Cu3O7-d

Scanning tunneling spectroscopy was performed on (110)-oriented thin films of Ca-overdoped Y

High quality a-axis outgrowth on c-axis Y1−xCaxBa2Cu3O7−δ

_{0.95}

Tunneling into YBCO Superconductor at High Magnetic Field

Ca

Origin of Hysteretic Field Splitting of the Zero Bias Conductance Peak in (100) and (110) Oriented Y1Ba2Cu3O7−x Films

_{0.05}

Tunneling spectroscopy: A probe for high-Tc superconductivity

Ba