Hideaki Nakane

DC-SQUID with High-Critical-Temperature Oxide-Superconductor Film

Voltage vs magnetic-flux characteristics of a DC-SQUID using YBa2Cu3O7-δ film have been studied. YBa2Cu3O7-δ film SQUID was fabricated by lithographical patterning. The DC-SQUID operated up to 72 K.

Light Detection by Superconducting Weak Link Fabricated with High-Critical-Temperature Oxide-Superconductor Film

The light-induced changes in the current-voltage characteristics are studied for a superconducting weak link fabricated with a polycrystalline YBa2Cu3O7-δ film. The maximum superconducting current decreases by exposure to light at temperatures up to 77 K. The sensitivity of the light detection is enhanced by the use of a photoconductive semiconductor film on the surface of the weak link.

A 4-bit Josephson data processor chip

The authors describe a 4-bit Josephson data processor chip featuring on-chip control and data paths and near-GHz capability. It is a closed, stand-alone chip comprising a 4-bit data path and a control path and is aimed at high-speed digital signal processing. The die is 0.5 mm square, including pads, is fabricated using 2.5- mu m-rule Nb/AlO/sub x//Nb technology, and consists of 8454 Josephson junctions and 9027 resistors. The cross-shaped junction structure realizes critical current scattering of +or-6%, and a junction characteristic voltage V/sub m/ of 50 mV. A block diagram of the Josephson data processor is shown.<<ETX>>

Operation of logic gate using YBa2Cu3O7−x/Ag/Pb‐In superconducting weak links

A logic gate has been fabricated with the partial use of high‐temperature superconducting films and tested to study digital applications of such films. The logic gate consists of three YBa2Cu3O7−x/Ag/Pb‐In superconducting weak links and three inductors. The current‐voltage characteristics of the weak links are nonhysteristic. The logic gate successfully provides and and or logic results for two external digital inputs at 4.2 K.

Josephson point contact using high-critical-temperature oxide-superconductors

The current-voltage characteristics of Josephson point contacts, Nb/YBa2Cu3O7-δ and YBa2Cu3O7-δ/YBa2Cu3O7-δ, are studied. At temperatures up to 40 K, nonlinear characteristics due to dc Josephson effect are observed for the YBa2Cu3O7-δ/YBa2Cu3O7-δ point contacts. The effect of thermal fluctuation on dc Josephson effect is discussed in comparison with experimental results.

DC-SQUID Using High-Critical-Temperature Oxide Superconductors

Voltage vs magnetic-flux characteristics of a DC-SQUID composed of YBa2Cu3O7-δ/YBa2Cu3O7-δ Josephson point contacts were studied. The DC-SQUID was operated up to 70 K.

Study of superconducting proximity effect by measuring interference effect of Andreev‐reflected quasiparticles

The change in pair potential for the Al‐Nb proximity system is reconstructed by measuring the dependence of differential resistance on incident energy using a lithographic point contact on the Al‐Nb bilayer. The bound states due to the interference effect of Andreev‐reflected quasiparticles, shift to higher‐energy levels. This can be explained by the position dependence of the pair potential near the Al‐Nb interface.