Anomalous quantum vortices in superconductor-ferromagnet devices

We introduce Josephson anomalous vortices (JAV), a new type of superconducting vortex which appears in Josephson junctions where the weak link is a ferromagnetic metal with strong spin-orbit coupling. JAVs are distinguished from other superconducting vortices as they do not arise due to a winding or a kink in the superconducting phase. They appear at zero-bias, in junctions of a length and width around a coherence length. Typically, superconducting magnetoelectric effects such as vortices arise due to a Lifshitz invariant in the Ginzburg-Landau free energy. In the systems studied here there is no Lifshitz invariant as the magnetisation is out-of-plane. We identify instead a new term in the Ginzburg-Landau free energy which gives rise to JAVs. We suggest that JAVs could be manipulated using spintronics techniques to write domain walls into the weak link, and detected via high-resolution magnetic probes, such as scanning-SQUID methods.