Properties of Intrinsic Josephson Junctions in Bi2Sr2CaCu2O8+δ Single Crystals

Minoru SUZUKI  Shin-ichi KARIMOTO  

IEICE TRANSACTIONS on Electronics   Vol.E81-C   No.10   pp.1518-1525
Publication Date: 1998/10/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: INVITED PAPER (Special Issue on Low- and High-Temperature Superconductive Electron Devices and Their Applications)
Category: High-Tc Junction Technology
high-Tc superconductors,  Bi2Sr2CaCu2O8+δ,  intrinsic Josephson junction,  gap parameter,  temperature dependence of Josephson current,  

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We describe several properties of very thin stacks of 10 to 20 intrinsic Josephson junctions fabricated on the surface of Bi2Sr2CaCu2O8+δ single crystals. We show that the Joule heating is significantly reduced in these stacks and that the gap structure is clearly observable in the quasiparticle current-voltage (I-V) characteristics. The I-V curves are characterized by a large subgap conductance and a significant gap suppression due to the injection of quasiparticle current. It is found that the IcRn product of these intrinsic Josephson junction stacks is significantly small compared with that expected from the BCS theory. It is also found that there is a tendency that IcRn decreases with increasing c-axis resistivity. Both Ic and the gap voltage exhibit unsaturated temperature dependence at low temperatures. The behavior presents a sharp contrast to that of Josephson junctions made of conventional superconductors. The characteristics are discussed in relation to the d-wave symmetry of the order parameter.