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

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.Comment: 25 pages, 7 figures, submitted to Phys. Rev.

Suppressed Superconductivity of the Surface Conduction Layer in Bi2_2Sr2_2CaCu2_2O8+x_{8+x} Single Crystals Probed by {\it c}-Axis Tunneling Measurements

We fabricated small-size stacks on the surface of Bi$_2$Sr$_2$CaCu$_2$O$_{8+x}$ (BSCCO-2212) single crystals with the bulk transition temperature $T_c$$\simeq$90 K, each containing a few intrinsic Josephson junctions. Below a critical temperature $T_c'$ ($\ll$ $T_c$), we have observed a weakened Josephson coupling between the CuO$_2$ superconducting double layer at the crystal surface and the adjacent one located deeper inside a stack. The quasiparticle branch in the $IV$ data of the weakened Josephson junction (WJJ) fits well to the tunneling characteristics of a d-wave superconductor($'$)/insulator/d-wave superconductor (D$'$ID) junction. Also, the tunneling resistance in the range $T_c'$$<$$T$$<$$T_c$ agrees well with the tunneling in a normal metal/insulator/d-wave superconductor (NID) junction. In spite of the suppressed superconductivity at the surface layer the symmetry of the order parameter appears to remain unaffected.Comment: 13 pages, 6 figure

Design of a Satellite Cluster System in Distributed Simulation

This article presents the design and development of a satellite cluster system that supports an interfederation communication in High Level Architecture (HLA)-compliant distributed simulation. The interfederation communication enables the execution of a complex, large-scale cluster system of distributed satellites that share the dispersed data assets among satellite components collaboratively. After a brief review of the HLA bridge for interfederation communication, the authors discuss the design issues related to a satellite cluster system that provides cluster management, interfederation communication, and communication data management. They analyze system performance and scalability for centralized and decentralized configurations. The empirical results on the heterogeneous OS distributed system indicate that the satellite cluster system is effective and scalable due to the use of interfederation communication and the reduction of data transmission

Design of a Satellite Cluster System in Distributed Simulation

This article presents the design and development of a satellite cluster system that supports an interfederation communication in High Level Architecture (HLA)-compliant distributed simulation. The interfederation communication enables the execution of a complex, large-scale cluster system of distributed satellites that share the dispersed data assets among satellite components collaboratively. After a brief review of the HLA bridge for interfederation communication, the authors discuss the design issues related to a satellite cluster system that provides cluster management, interfederation communication, and communication data management. They analyze system performance and scalability for centralized and decentralized configurations. The empirical results on the heterogeneous OS distributed system indicate that the satellite cluster system is effective and scalable due to the use of interfederation communication and the reduction of data transmission