# Effect of surface on the conductance characteristics of $Au-Bl_2Sr_2CaCu_20_{8+\delta}$ (single crystal) point contact junctions

Srikanth, H and Raychaudhuri, AK (1991) Effect of surface on the conductance characteristics of $Au-Bl_2Sr_2CaCu_20_{8+\delta}$ (single crystal) point contact junctions. In: Journal of Applied Physics, 70 (12). pp. 7478-7483.

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## Abstract

We report the effect of surface treatments on the dynamic conductance curves (G=dI/dV-V) of $Au-Bi_2Sr_2CaCu_2O_{8+\delta}$ (single crystal) point contact junctions of variable junction conductances (100 mS>G>100 \mu S). We find that if the crystal surface is cleaved freshly just prior to making contacts, all irreproducible sharp multiple features often observed in tunneling data of Bi(2212) oxide superconductors disappear. If the cleaved crystal surfaces are left under ambient conditions for a few days and the tunneling experiments are repeated, these multiple features reappear. We also find that if the current in the junction is made to pass predominantly through the bulk (and not along the surface), gap features are sharper. The observed conductance curves are fitted to a modified model [G. E. Blonder et al., Phys. Rev. B 25, 4515 (1982)] and estimated gap values are \Delta\simeq28 to 30 meV corresponding to the ratio $2\Delta/k_BT_c$ \simeq 7.5 with lifetime broadening \Gamma/\Delta\simeq0.2. We conclude that the sharp multiple features observed in Bi(2212) tunneling curves has no intrinsic origin in the bulk and they arise from the surface only.

Item Type: Journal Article Copyright of this article belongs to the American Institute of Physics. Division of Physical & Mathematical Sciences > Physics 11 Mar 2008 19 Sep 2010 04:43 http://eprints.iisc.ernet.in/id/eprint/13363