Superconductivity at ferromagnetic domain walls in hybrid InAs/EuS/Al nanowires, part 1: studied by scanning SQUID imaging

Ferromagnet/superconductor heterostructures are playgrounds for novel quantum phases that rarely occur naturally in nature, e.g. topological, spin-triplet, etc. One particularly intriguing example is the possible signature of Majorana fermions recently observed in EuS/InAs/Al nanowires. While ferromagnetism normally precludes superconductivity, Cooper pairing may survive in proximity to magnetic domain walls. Heterostructure nanowires are particularly suitable for studying such domain wall superconductivity as their high aspect ratio encourages domain formation only along the length alleviating averaging effects from neighbouring domains. In this talk I will present magnetometry images taken using scanning Superconducting QUantum Interference Device (SQUID) to explore magnetic domain formation in full shell InAs/EuS/Al nanowires as we sweep a full in-plane hysteresis loop at 4 K at a range of field angles. We use our magnetometry images to explain the observation of superconductivity in magneto-transport measurements, which will be presented in the second part of this talk.