Hydrogen-impurity-induced conductance peaks in constriction type Josephson junctions

Kazuki Miyakawa, Hiroki Takata, Taishi Yamaguchi, Yuji Inagaki, Kazumasa Makise and Tatsuya Kawae

We studied hydrogen (H) and deuterium (D) impurity effects of superconducting Josephson current flowing through the superconductor-constriction-superconductor Josephson junctions (ScS-JJ). When H or D impurities are adsorbed on the surface of the ScS-JJ prepared by niobium or lead, many spike-like peaks with almost the same spacing appear inside the superconducting gap in addition to anomalies owing to the multiple Andreev reflection in the differential conductance spectra. The spacing between the adjacent peaks is independent of the temperature variation. These indicate that H or D impurities adsorbed on the JJ are sources of noise for the Josephson current.

Applied Physics Express

15

013002