Speaker
Description
We discuss a discrete model of an annular array of underdamped superconductor—ferromagnet—superconductor $\varphi_0$ Josephson junctions. In this model, the anomalous $\varphi_0$ phase shift arises because of the superconducting proximity effect in the magnetic layer with broken inversion symmetry. It produces a bi-directional, direct coupling between the superconducting part of the applied bias current and the magnetic moment within the ferromagnetic material. Here, we include for the first time the effective field, felt by the magnetisation, due to the surface and fluxon-induced currents. We show that this additional coupling can lead to the occurrence of chaos and magnetisation `spin’ waves within the ferromagnetic interlayer. As in other models of Josephson metamaterials, the occurrence of chaos in the present model is not particularly desirable for potential spintronic applications; however, the magnetisation waves, which lead to a reduced critical current in the junction and change the branching structure of the zero-field steps, could potentially improve the efficiency of single-photon detectors for qubit readout.