Robustness of Majorana fermions in proximity-induced superconductors

Abstract

In two-dimensional chiral p-wave superconductors, the zero-energy Majorana fermion excitations trapped at vortex cores are protected from the thermal effects by the minigap, Δ2/ϵF (Δ: bulk gap, ϵF: Fermi energy), which is the excitation gap to the higher energy bound states in the vortex cores. Robustness to thermal effects is guaranteed only when T⪡Δ2/ϵF∼0.1 mK, which is a very severe experimental constraint. Here we show that when s-wave superconductivity is proximity-induced on the surface of a topological insulator or a spin-orbit-coupled semiconductor, as has been recently suggested, the minigaps of the resultant non-Abelian states can be orders of magnitude larger than in a chiral p-wave superconductor. Specifically, for interfaces with sufficient barrier transparencies, the minigap can be as high as ∼Δ⪢Δ2/ϵF, where Δ is the bulk gap of the s-wave superconductor.

Source-reported materials — not catalogue approval

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