Non-Fraunhofer Interference Pattern in Inhomogeneous Ferromagnetic Josephson Junctions

TL;DR

This paper theoretically demonstrates how inhomogeneities in ferromagnetic Josephson junctions lead to a non-Fraunhofer interference pattern in the critical supercurrent, explaining recent experimental observations.

Contribution

It establishes generic conditions for non-Fraunhofer patterns in ferromagnetic Josephson junctions using the quasiclassical Keldysh-Usadel method, highlighting the role of inhomogeneities.

Findings

Inhomogeneity in energy scales drastically alters the interference pattern.

Non-Fraunhofer response is linked to multiple '0-pi'-states and proximity vortices.

Theoretical results match recent experimental observations.

Abstract

Generic conditions are established for producing a non-Fraunhofer response of the critical supercurrent subject to an external magnetic field in ferromagnetic Josephson junctions. Employing the quasiclassical Keldysh-Usadel method, we demonstrate theoretically that an inhomogeneity in the magnitude of the energy scales in the system, including Thouless energy, exchange field and temperature gradient normal to the transport direction, influences drastically the standard Fraunhofer pattern. The exotic non-Fraunhofer response, similar to that observed in recent experiments, is described in terms of an intricate interplay between multiple '0-pi'-states and is related to the appearance of proximity vortices.