Determination of the critical current density in the dwave superconductor YBCO under appli.pdf
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Determination of the critical current density in the d-wave superconductor
YBCO under applied magnetic fields by nodal tunneling
Roy Beck, Guy Leibovitch, Alexander Milner, Alexander Gerber and Guy Deutscher
School of Physics and Astronomy, Raymond and Beverly Sackler faculty of Exact
Sciences, Tel-Aviv University, 69978 Tel-Aviv, Israel
PACS: 74.25.Sv, 74.50.+r, 74.72.Bk
Abstract
We have studied nodal tunneling into YBa Cu O (YBCO) films under magnetic
2 3 7-x
fields. The films orientation was such that the CuO planes were perpendicular to the
2
0
surface with the a and b axis at 45 form the normal. The magnetic field was applied
parallel to the surface and perpendicular to the CuO2 planes. The Zero Bias
Conductance Peak (ZBCP) characteristic of nodal tunneling splits under the effect of
surface currents produced by the applied fields. Measuring this splitting under
different field conditions, zero field cooled and field cooled, reveals that these
currents have different origins. By comparing the field cooled ZBCP splitting to that
taken in decreasing fields we deduce a value of the Bean critical current superfluid
. 7 2
velocity, and calculate a Bean critical current density of up to 3 10 A/cm at low
temperatures. This tunneling method for the determination of critical currents under
magnetic fields has serious advantages over the conventional one, as it avoids having
to make high current contacts to the sample.
As shown by de Gennes and Saint James (1), finite energy bound states are formed in
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