Signatures of Majorana bound states in scanning gate microscopy of hybrid nanowires

Abstract

We theoretically study scanning gate microscopy of a superconductor-proximitized semiconducting wire focusing on the potential for detection of Majorana bound states. We exploit the possibility to create a local potential perturbation by the scanning gate tip which allows controllable modification of the spatial distribution of the Majorana modes, which is translated into changes in their energy structure. When the tip scans across the system, it effectively divides the wire into two parts with controllable lengths, in which two pairs of Majorana states are created when the system is in the topological regime. For strong values of the tip potential, the pairs are decoupled, and the presence of Majorana states can be detected via local tunneling spectroscopy that resolves the energy splittings resulting from the Majorana states wave functions overlap. Importantly, as the system is probed spatially via the tip, this technique can distinguish Majorana bound states from quasi-Majorana states localized on smooth potential barriers. We demonstrate that for weaker tip potentials, the two neighboring Majorana states hybridize, opening pronounced anticrossings in the energy spectra which are reflected in local conductance maps and which result in non-zero non-local conductance features. Finally, we demonstrate that the scanning gate microscopy technique can be used to discriminate between the trivial and topological nature of the zero-bias conductance peak in disordered wires.