Flux-induced Majorana modes in full-shell nanowires*

We demonstrate a novel means of creating Majorana zero modes using magnetic flux applied to a full superconducting shell surrounding a semiconducting nanowire core, unifying approaches based on proximitized nanowires and vortices in topological superconductors. In the destructive Little-Parks regime, reentrant regions of superconductivity are associated with an integer number of phase windings in the shell. Tunneling into the core reveals a hard induced gap near zero applied flux, corresponding to zero phase winding, and a gapped region with a discrete zero-energy state for flux around $\Phi_{0} = h/2e$, corresponding to $2 \pi$ phase winding. Coulomb peak spacing in full-shell islands around one applied flux shows exponentially decreasing deviation from $1e$ periodicity with device length, consistent with the picture of Majorana modes located at the ends of the wire.

https://arxiv.org/abs/1809.05513