Josephson voltage standards

Abstract

This paper reviews the present state of modern Josephson voltage standards. The presentation focuses on conventional dc standards based on underdamped superconductor-insulator-superconductor junctions and programmable standards based on overdamped superconductor-insulator-normal conductor-insulator-superconductor junctions. The current developments of ac standards on the basis of pulse-driven arrays and single flux quantum-based voltage multipliers are briefly summarized.

Towards precise measurement of oscillatory domain wall by ferromagnetic Josephson junction

“…31 On the other hand, V is precisely determined by the conventional Josephson junction in the order of 10 −9 accuracy. 20,21 Hence, the measurement on V can determine the DW frequency precisely. Accuracy of conventional measurement on the DW oscillation is limited in order of about 10 −2 ∼ 10 −3 , since those methods depend on material parameters such as anisotropic field, saturation magnetization and so on.…”

“…18 Under irradiation of microwave to the Josephson junction, the current-voltage (I-V ) curve shows step structures at V = n( /2e)ν with microwave frequency ν, integer n, and the ratio of the Plank constant and the elementary charge /e. This structure called Shapiro step 19 is adopted to the voltage standard around the world, 20,21 since the voltage can be determined in the order of 10 −9 accuracy by the precise values of the frequency and the fundamental constants. 20,21 On the other hand, many authors studied the Josephson effect in a hybrid structure of superconductor and ferromagnet.…”

“…This structure called Shapiro step 19 is adopted to the voltage standard around the world, 20,21 since the voltage can be determined in the order of 10 −9 accuracy by the precise values of the frequency and the fundamental constants. 20,21 On the other hand, many authors studied the Josephson effect in a hybrid structure of superconductor and ferromagnet. [22][23][24][25][26][27] In this ferromagnetic Josephson junction (FJJ), two superconducting electrodes are separated by a thin ferromagnetic layer, whose thickness is controlled in the order of nano meter.…”

Development of Josephson voltage standards

“…This chapter describes the development of these modern dc and ac Josephson voltage standards as well as their fundamentals and applications. The development and use of Josephson voltage standards have also been described recently in several review papers (amongst others : Niemeyer, 1998;Hamilton, 2000;Yoshida, 2000;Behr et al, 2002;Kohlmann et al, 2003;Benz & Hamilton, 2004;Jeanneret & Benz, 2009). …”

Possible method to observe the breathing mode of a magnetic domain wall in the Josephson junction

“…Superconducting quantum interference devices (SQUIDs) presently offer the highest sensitivity to a magnetic field. The Josephson junction under irradiation of microwave provides a precise value of voltage adopted to the voltage standard 22,23 . In the latter case, the current-voltage (I-V ) curve shows step structures at the voltage V = n( /2e)f with microwave frequency f , integer n, and the ratio of the Planck constant and the elementary charge /e.…”