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A comparison of barrier type tunnel junction and point contact tunnel junction formed on the same high $T_c$ material

Srikanth, H and Raychaudhuri, AK (1991) A comparison of barrier type tunnel junction and point contact tunnel junction formed on the same high $T_c$ material. In: Pramana, 36 (6). pp. 621-627.


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By making a combination of both point contact and barrier type tunnel junctions on a single sample of the high $T_c$ superconductor BSCCO (2212) single crystal, we have shown that as the tunneling tip is slowly retracted from the surface a point contact junction gradually evolves from a N-S short to a high resistance tunnel junction. The scaled dynamic conductance (dl/dV) of this point contact tunnel junction becomes almost identical to that of a conventional barrier type tunnel junction and both show a linear dl/dV — V curve. The observation implies that at high resistance a point contact junction behaves in the same way as a barrier type tunnel junction. We suggested that the almost linear tunneling conductance obtained in both the cases most likely arises due to an intrinsic characteristic of the surface of the crystal comprising of a mosaic of superconducting regions of the order of a few nanometers. We also conclude that the barrierless (N-S) point contact obtained by piercing the surface oxide layer of the crystal shows Andreev reflection which we suggest as the origin of the zero bias anomaly often observed in point contact junctions.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to Indian Academy of Sciences.
Keywords: Point contact;Tunneling;Cryogenic scanning tunneling microscope;Andreev reflection;Oxide superconductors
Department/Centre: Division of Physical & Mathematical Sciences > Physics
Depositing User: Dipti Chaurasia
Date Deposited: 03 Nov 2006
Last Modified: 19 Sep 2010 04:32
URI: http://eprints.iisc.ac.in/id/eprint/8717

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