DC Superconducting Quantum Interference Device Utilizing the High Tc Step-Edge Junction

Abstract
An artificial step-edge junction for developing the high T c weak links is presented. The step-edge junction is fabricated by using the step edge of the double layer of the epitaxial YBaCuO films. The dc superconducting quantum interference device (SQUID) made of the junction shows a clear voltage-vs-flux (V-Φ) relation up to T=81.3 K. The voltage modulation depth ΔV of the V-Φ relation is ΔV=1.6 µV at T=77 K. A preliminary experiment shows that the magnetic-flux noise of the SQUID at T=77 K is, at most, Φ n =4.4×10-4Φ0/√Hz at f=10 Hz. These results show the promising properties of the step-edge junction for the weak link of high T c superconductors.
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