Extrinsic spin-orbit coupling in hybrid nanowires with micromagnet arrays

Arrays of anti-aligned micromagnets have been proposed as a way to generate rotating magnetic fields which can induce both an extrinsic spin-orbit coupling and Zeeman splitting in superconducting-semiconductor nanowires. This technique has the potential to widen the range of materials that can host Majorana modes to include low-disorder materials like carbon nanotubes or silicon nanowires, as well as enhance the topological protection available in existing materials by adding to their intrinsic spin-orbit coupling. We demonstrate the preparation of micromagnet arrays into the anti-aligned micromagnetic configuration using a sequence of externally applied magnetic fields. Measurements using bias spectroscopy show micromagnetic configuration dependence in a hybrid nanowire superconducting island . Low bias features of the superconducting island are consistent with the presence of a subgap state in the nanowire with a 25µeV difference in subgap state energy between anti-aligned and aligned micromagnetic configurations.