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Surface impedance of YBa 2Cu 3O 7/Y 0.6Pr 0.4Ba 2Cu 3O 7 bilayers: Possible evidence for the proximity effect

Summary: Surface impedance of YBa 2Cu 3O 7/Y 0.6Pr 0.4Ba 2Cu 3O 7 bilayers:
Possible evidence for the proximity effect
Michael S. Pambianchi,* C. Kwon, T. Venkatesan, and Steven M. Anlage
Center for Superconductivity Research, Department of Physics, University of Maryland, College Park, Maryland 20742-4111
Received 1 August 1996
Measurements of the surface impedance of superconductor/normal-metal bilayers provide information
on the proximity coupling between superconductors with different transition temperatures. Surface im-
pedance data on c-axis YBa2Cu3O7 /Y0.6Pr0.4Ba2Cu3O7 bilayers is consistent with either proximity
coupling in the c direction between the two materials with a very weak proximity-induced condensate and/or
the behavior of two isolated superconductors in a bilayer geometry. At least one of the characteristics of
proximity coupled superconductors, namely, a strong downturn of the effective penetration depth above the
lower of the two transition temperatures, was not observed in the c-axis high-Tc bilayer films studied. How-
ever, the increase of the surface resistance above the Tc of the Pr-doped layer is a sign that the conductivity of
the Y0.6Pr0.4Ba2Cu3O7 layer is strongly enhanced above its Tc , in agreement with THz spectroscopy mea-
surements. S0163-1829 96 03645-4
Although the superconducting proximity effect has been
amply demonstrated in low-Tc superconductor/normal-metal
bilayer systems, there is little evidence of this effect in high-
Tc cuprate superconductors. Reasons for this lack of evi-


Source: Anlage, Steven - Center for Superconductivity Research & Department of Physics, University of Maryland at College Park


Collections: Materials Science