Accurate measurements of quantum voltage steps on arrays of bicrystal Josephson junctions

Abstract

Quantum voltages of an array of YBa 2 Cu 3 O 7 bicrystal junctions were calibrated against a programmable Josephson array voltage standard. We demonstrated that steps of the current-voltage characteristic of an array of bicrystal junctions at voltages of about 9 mV were flat over the current range of about 80 A to within six parts in 10 8 . The coincidence of quantum voltages on the array of high-temperature superconductor junctions at 64 K and the reference voltage on the array of niobium junctions at 4.2 K was measured with an uncertainty of two parts in 10 8 . With the same uncertainty, we revealed the coincidence of the Josephson constant K J ϵh/2e in YBa 2 Cu 3 O 7 and in metallic superconductors.

DC voltage calibrator based on an array of high-temperature superconductor josephson junctions

“…Recently, quantum voltages of an array of YBCO bicrystal junctions were calibrated against a programmable Josephson array voltage standard of the Physikalisch-Technische Bundesanstalt [6]. The coincidence of quantum voltages of the array of HTS junctions at 64 K and of the array of niobium junctions at 4.2 K was shown within an uncertainty of 1.7 parts in 10 .…”

Josephson junctions with nearly superconducting metal silicide barriers

“…The superconductor-normal metal-superconductor junction, 2,3 in which a normal metal is sandwiched between two superconductors, is the most common intrinsically shunted junction system for these latter applications. [4][5][6] However, in some cases, the barrier material is also a superconductor with a transition temperature lower than either of the electrodes and lower than the operating temperature; 7 this is typically called an SS'S junction structure. In our search for improved Nb-based junctions for voltage standard applications we have found two such barrier materials with excellent characteristics, TiSi 2 and WSi 2 .…”

Zero-crossing Shapiro step generated in a niobium in-line Josephson gate

“…The critical currentmagnetic field characteristics of a long JJ over a superconducting ground plane (GP) become tilted owing to the Meissner effect of the GP, which would allow us to generate a ZCSS as well. From another perspective, a single but long JJ is regarded as a simulated model of a YBa 2 Cu 3 O 7−δ (YBCO) grain boundary (GB) JJ that would be applied for future voltage standards operated at 60 K or over [12,13].…”