Influence of disorder on vortex Majorana states in 3D topological insulators

Majorana states hosted in vortex cores of topological insulator/superconductor

heterostructures present a promising alternative to nanowire-based approaches.

Vortices can be pinned to anti-dots pre-fabricated in the superconductor; large anti-

dots are relatively simple to fabricate and ensure that weak magnetic fields are

sufficient to induce a required quantum of flux. However, it has thus far been unclear

whether current topological insulator materials are clean enough to sustain Majorana

vortex modes with a sizable gap to excitations. In this talk, I will present our numerical

studies of the vortex subgap spectrum as a function of disorder, chemical potential,

and the anti-dot size. We employ a two-dimensional low-energy description of the

topological insulator surface, which allows us to simulate large system sizes with

vortices up to 1 micron in diameter. We connect our results to existing mobility

measurement data to translate the level of disorder in existing materials to our

simulated disorder model.