Deconfinement of Majorana vortex modes produces a superconducting Landau level

TL;DR

This paper demonstrates that a specific oscillating pair potential can deconfine Majorana modes in a topological insulator heterostructure, leading to a protected Landau level detectable via local density of states oscillations.

Contribution

It introduces a mechanism for Majorana deconfinement via oscillating pair potential and predicts a resulting Landau level in a Fu-Kane heterostructure.

Findings

Majorana modes deconfine with oscillating pair potential K > Δ₀/ħv.

Deconfined Majoranas form a dispersionless Landau level.

Local density of states oscillates with a measurable wave vector.

Abstract

A spatially oscillating pair potential $\Delta(r)=\Delta_0 e^{2i K\cdot r}$ with momentum $K>\Delta_0/\hbar v$ drives a deconfinement transition of the Majorana bound states in the vortex cores of a Fu-Kane heterostructure (a 3D topological insulator with Fermi velocity $v$, on a superconducting substrate with gap $\Delta_0$, in a perpendicular magnetic field). In the deconfined phase at zero chemical potential the Majorana fermions form a dispersionless Landau level, protected by chiral symmetry against broadening due to vortex scattering. The coherent superposition of electrons and holes in the Majorana Landau level is detectable as a local density of states oscillation with wave vector $\sqrt{K^2-(\Delta_0/\hbar v)^2}$. The striped pattern also provides a means to measure the chirality of the Majorana fermions.