Suppressed Superconductivity of the Surface Conduction Layer in Bi$_2$Sr$_2$CaCu$_2$O$_{8+x}$ Single Crystals Probed by {\it c}-Axis Tunneling Measurements

Nam Kim; Yong Joo Doh; Hyun-Sik Chang; Hu-Jong Lee

doi:10.1103/PhysRevB.59.14639

paper

Suppressed Superconductivity of the Surface Conduction Layer in Bi $_{2}$ Sr $_{2}$ CaCu $_{2}$ O $_{8 + x}$ Single Crystals Probed by {\it c}-Axis Tunneling Measurements

arXiv:cond-mat/9808102 · doi:10.1103/PhysRevB.59.14639

Abstract

We fabricated small-size stacks on the surface of Bi $_{2}$ Sr $_{2}$ CaCu $_{2}$ O $_{8 + x}$ (BSCCO-2212) single crystals with the bulk transition temperature $T_{c}$ $≃$ 90 K, each containing a few intrinsic Josephson junctions. Below a critical temperature $T_{c}^{'}$ ( $≪$ $T_{c}$ ), we have observed a weakened Josephson coupling between the CuO $_{2}$ superconducting double layer at the crystal surface and the adjacent one located deeper inside a stack. The quasiparticle branch in the $I V$ data of the weakened Josephson junction (WJJ) fits well to the tunneling characteristics of a d-wave superconductor( $^{'}$ )/insulator/d-wave superconductor (D $^{'}$ ID) junction. Also, the tunneling resistance in the range $T_{c}^{'}$ $<$ $T$ $<$ $T_{c}$ agrees well with the tunneling in a normal metal/insulator/d-wave superconductor (NID) junction. In spite of the suppressed superconductivity at the surface layer the symmetry of the order parameter appears to remain unaffected.

13 pages, 6 figures

Suppressed Superconductivity of the Surface Conduction Layer in Bi2​Sr2​CaCu2​O8+x​ Single Crystals Probed by {\it c}-Axis Tunneling Measurements

Abstract

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Suppressed Superconductivity of the Surface Conduction Layer in Bi $_{2}$ Sr $_{2}$ CaCu $_{2}$ O $_{8 + x}$ Single Crystals Probed by {\it c}-Axis Tunneling Measurements