Phys. Rev. Lett. 122, 126801 (2019)

Majorana fermions can emerge from so-called p-wave topological superconductors. This superconducting state is known to be very fragile — it takes only a small amount of disorder to break it up. But, Arbel Haim and Ady Stern have suggested a material where disorder might actually help to make Majoranas more stable.

They model a Josephson junction where the weak link is made from a semiconductor with spin–orbit coupling. An analysis of the modes in the weak link shows that those most relevant for the superconductivity have the largest momentum, and hence the strongest spin–orbit coupling. This means that modes with opposite momentum have opposite spin, so ‘backscattering’ between them is suppressed. In turn, this means that the effective superconducting gap is enhanced for these channels, forcing any Majoranas that might emerge from them to be localized more strongly at the end of the Josephson junction, and hence be more robust.