Nd/sub 1.85/Ce/sub 0.15/CuO/sub 4-y/ bicrystal grain boundary Josephson junctions

Abstract

The study of the detailed influence of the order parameter (OP) symmetry on the properties of high temperature superconducting (HTS) Josephson junctions still is a key issue. Whereas the hole doped HTS such as YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (YBCO), Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8+x/ (BSCCO), or La/sub 1.85/Sr/sub 0.15/CuO/sub 4-/spl delta// (LSCO) are known to have a dominating d-wave component of the OP, there is significant evidence that the electron doped material Nd/sub 1.85/Ce/sub 0.15/CuO/sub 4-y/ (NCCO) has an s-wave symmetry of the OP. Therefore, we have studied the electrical transport properties of [001] tilt NCCO bicrystal grain boundary Josephson junctions (GBJs) with misorientation angles between 7/spl deg/ and 36.8/spl deg/ and compared them to those of the hole doped HTS. For the NCCO-GBJs an exponential decay of the critical current density J/sub c/ with increasing misorientation angle as well as a scaling of the characteristic junction voltage V/sub c//spl prop/J/sub c//sup p/ was found very similar to what is observed for the hole doped HTS. This strongly suggests that the OP symmetry is not the key parameter controlling the characteristic properties of HTS-GBJs. In contrast, they are most likely related to the presence of a disorder induced, insulating grain boundary barrier which is similar for both the d- and s-wave HTS.