# Microshort-to-tunneling transition in $Au-YBa_2Cu_3O_{7-\delta}$ single-crystal point contacts

Srikanth, H and Raychaudhuri, AK (1992) Microshort-to-tunneling transition in $Au-YBa_2Cu_3O_{7-\delta}$ single-crystal point contacts. In: Physical Review B: Condensed Matter and Materials Physics, 45 (1). pp. 383-388.

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## Abstract

We report on the evolution of dynamic conductance curves [(dI/dV)-V] as a function of junction resistance in $Au-YBa_2Cu_3O_{7-\delta}$ single-crystal point-contact junctions. We have demonstrated that it is possible to evolve continuously from a microshort (N-S) to a tunnel junction (N-I-S) by adjusting the contact pressure in the point-contact junction. At the lowest junction resistances, we see a peak in dI/dV at zero bias, which we explain as due to Andreev reflection. As the junction resistance is gradually increased, the zero-bias peak diminishes and gaplike features appear in the (dI/dV)-V curves. At even higher resistance, the zero-bias peak vanishes, all features get smeared out, and a linear dI/dV variation with the bias voltage is seen. Based on the similarity of (dI/dV)-V curves obtained in high-resistance $Au-YBa_2Cu_3O_{7-\delta}$ junctions with those obtained in a nonsuperconducting perovskite oxide metal ($Au-Na_xWO_3$ junctions, x$\simeq$0.45), we suggest that the linear (dI/dV)-V curves arise due to inelastic scattering of electrons at a ‘‘metallic’’ layer on the surface of the superconductor.

Item Type: Journal Article Copyright of this article belongs to The American Physical Society Microshort-to-tunneling transition;dynamic conductance curves;superconductor Division of Physical & Mathematical Sciences > Physics 26 Mar 2008 19 Sep 2010 04:43 http://eprints.iisc.ernet.in/id/eprint/13490