Chiral Majorana Fermion Modes on the Surface of Superconducting Topological Insulators

TL;DR

This paper demonstrates the simulation of chiral Majorana modes on the surface of superconducting topological insulators, showing their dependence on magnetic islands and chemical potential tuning, with implications for quantum computing applications.

Contribution

It introduces a realistic tight-binding simulation of CMMs on STI surfaces, revealing conditions for their emergence and tunability via exchange coupling and chemical potential adjustments.

Findings

CMMs appear on ferromagnetic island edges after superconducting gap inversion.

Multiple CMMs can be generated by tuning the chemical potential.

Results applicable to both proximity-induced and intrinsic topological insulators.

Abstract

The surface of superconducting topological insulators (STIs) has been recognized as an effective $p\pm ip$ superconductivity platform for realizing elusive Majorana fermions. Chiral Majorana modes (CMMs), which are different from Majorana bound states localized at points, can be achieved readily in experiments by depositing a ferromagnetic overlayer on top of the STI surface. Here we simulate this heterostructure by employing a realistic tight-binding model and show that the CMM appears on the edge of the ferromagnetic islands only after the superconducting gap is inverted by the exchange coupling between the ferromagnet and the STI. In addition, multiple CMMs can be generated by tuning the chemical potential of the topological insulator. These results can be applied to both proximity-effect induced superconductivity in topological insulators and intrinsic STI compounds such as PbTaSe$_2$, BiPd and their chemical analogues, providing a route to engineering CMMs in those materials.