Figure 1
Experimental setup for a Majorana ladder. (a) Illustration of a pair of Majorana fermions (red dots) embedding respectively in the top and bottom of a vortex line (green tube) in a strong-topological-insulator thin film (STI, light-blue region) on an s-wave superconductor (S, dark-blue regions). (b) An array of vortices in the heterostructure, forming a two-leg Majorana ladder. An applied magnetic field B (dashed arrow) lines up vortices with angle θ and hence tilts the ladder system. (c) The tight-biding model for the Majorana ladder, describing top-chain (γ) and bottom-chain (λ) Majorana fermions coupled by intra-leg tunnelings t 1 γ i γ i+1 and t 2 λ i λ i+1, inter-leg tunnelings t s γ j λ j and t d λ j γ j+1, and four-Majorana interaction Uγ j λ j λ j+1 γ j+1.
