Progressive evolution of tunneling characteristics of in-situ fabricated intrinsic Josephson junctions in Bi_2Sr_2CaCu_2O_{8+delta} single crystals

TL;DR

This study systematically investigates the tunneling characteristics of intrinsic Josephson junctions in Bi-2212 single crystals using in-situ fabrication and measurement, revealing key scaling behaviors and effects of proximity contact.

Contribution

It introduces an in-situ etching and measurement technique that isolates intrinsic junction properties, clarifying effects of surface and inner planes without external parameter variations.

Findings

Tunneling resistance and I-V curves scale with surface junction resistance.

Surface gap and T_c reduction are due to proximity contact, not doping changes.

Main junction features are unaffected by neighboring junctions at low bias.

Abstract

Stacks of a few intrinsic tunnel junctions were micro-fabricated on the surface of Bi-2212 single crystals. The number of junctions in a stack was tailored by progressively increasing the height of the stack by ion-beam etching, while its tunneling characteristics were measured in-situ in a vacuum chamber for temperatures down to ~13 K. Using this in-situ etching/measurements technique in a single piece of crystal, we systematically excluded any spurious effects arising from variations in the junction parameters and made clear analysis on the following properties of the surface and inner conducting planes. First, the tunneling resistance and the current-voltage curves are scaled by the surface junction resistance. Second, we confirm that the reduction in both the gap and the superconducting transition temperature of the surface conducting plane in contact with a normal metal is not caused by the variation in the doping level, but is caused by the proximity contact. Finally, the main feature of a junction is not affected by the presence of other junctions in a stack in a low bias region.