Controllable magnetic states in chains of coupled phi-0 Josephson junctions with ferromagnetic weak links

TL;DR

This paper explores how chains of coupled phi_0 Josephson junctions with ferromagnetic links exhibit controllable magnetic states mediated by superconducting phases, enabling electrical control over magnetic configurations and interactions.

Contribution

It introduces a model for magnetic states in coupled phi_0-S/F/S Josephson junction chains, demonstrating electrical control over magnetic configurations and long-range interactions.

Findings

Magnetic states resemble an n-level system influenced by magnetoelectric coupling.

Total magnetic moment can be fully controlled by supercurrent.

System exhibits highly nonlocal response to external perturbations.

Abstract

A superconductor/ferromagnet/superconductor Josephson junction with anomalous phase shift (phi_0-S/F/S JJ) is a system, where the anomalous ground state shift phi_0 provides a direct magnetoelectric coupling between a magnetic moment and a phase of the superconducting condensate. If a chain of such phi_0-S/F/S JJs are coupled via superconducting leads, the condensate phase, being a macroscopic quantity, mediates a long-range interaction between the magnetic moments of the weak links. We study static and dynamic magnetic properties of such a system. It is shown that it manifests properties of n-level system, where the energies of the levels are only determined by projections of the total magnetic moment onto the easy magnetic axis. It is similar to a magnetic atom in a Zeeman field, but the role of the field is played by the magnetoelectric coupling. However, unlike an atom in a magnetic field, the relative order of energies of different states is controlled by electrical means. It is also demonstrated that the total magnetic moment can be fully controlled by a supercurrent and the response of the magnetic system to local external perturbations is highly nonlocal.