Self-field effects in window-type Josephson tunnel junctions

TL;DR

This paper revisits and extends the analysis of magnetic effects in Josephson tunnel junctions, focusing on how electrode properties influence the critical current diffraction patterns, with experimental validation of the theoretical models.

Contribution

It provides a generalized model for asymmetric diffraction patterns in window-type Josephson junctions considering electrode differences, supported by experimental data.

Findings

Asymmetry in diffraction patterns increases with electrode inductance differences.

Empirical expressions for electrode inductances are provided.

Experimental results agree with the extended theoretical model.

Abstract

The properties of Josephson devices are strongly affected by geometrical effects such as those associated with the magnetic field induced by the bias current. The generally adopted analysis of Owen and Scalapino [{\it Phys. Rev.}{\bf 164}, 538 (1967)] for the critical current, $I_c$, of an in-line Josephson tunnel junction in presence of an in-plane external magnetic field, $H_e$, is revisited and extended to junctions whose electrodes can be thin and of different materials. We demonstrate that the asymmetry of the magnetic diffraction pattern, $I_c(H_e)$, is ascribed to the different electrode inductances for which we provide empirical expressions. We also generalize the modeling to the window-type junctions used nowadays and discuss how to take advantage of the asymmetric behavior in the realization of some superconducting devices. Further we report a systematic investigation of the diffraction patterns of in-line window-type junctions having a number of diverse geometrical configurations and made of dissimilar materials. The experimental results are found in agreement with the predictions and clearly demonstrate that the pattern asymmetry increases with the difference in the electrode inductances.