Vortex Lines in Topological Insulator-Superconductor Heterostructures

TL;DR

This paper investigates the conditions under which Majorana fermions can be observed in topological insulator-superconductor heterostructures, emphasizing the roles of surface and bulk physics in their formation and stability.

Contribution

It clarifies when bulk effects influence Majorana modes versus when surface physics dominates in 3D topological insulator-superconductor systems.

Findings

Bulk penetrations can gap surface vortex modes, affecting Majorana fermions.

Surface physics can be isolated under certain conditions, preserving Majorana modes.

The role of bulk physics is crucial in the energy and location of Majorana modes.

Abstract

3D topological insulator/s-wave superconductor heterostructures have been predicted as candidate systems for the observation of Majorana fermions in the presence of superconducting vortices. In these systems, Majorana fermions are expected to form at the interface between the topological insulator and the superconductor while the bulk plays no role. Yet the bulk of a 3D topological insulator penetrated by a magnetic flux is not inert and can gap the surface vortex modes destroying their Majorana nature. In this work, we demonstrate the circumstances under which only the surface physics is important and when the bulk physics plays an important role in the location and energy of the Majorana modes.