Electrically tunable topological superconductivity and Majorana fermions in two dimensions

TL;DR

This paper predicts how electric fields can control Majorana fermions in two-dimensional topological superconductors, enabling tunable topological phases and potential experimental observation via scanning tunneling microscopy.

Contribution

It introduces a method to electrically tune topological superconductivity and Majorana fermions in 2D systems using a topological insulator thin film with ferromagnetic order.

Findings

Electric field induces topological quantum phase transition.

Majorana bound states can be observed at electric field boundaries.

Structure inversion asymmetry enlarges topological superconductor phases.

Abstract

The external controllability of topological superconductors and Majorana fermions would be important both for fundamental and practical interests. Here we predict the electric-field control of Majorana fermions in two-dimensional topological superconductors utilizing a topological insulator thin film proximity coupled to a conventional $s$-wave superconductor. With ferromagnetic ordering, the tunable structure inversion asymmetry by vertical electric field could induce topological quantum phase transition and realize a chiral topological superconductor state. A zero-energy Majorana bound state appears at the boundary of an applied electric field spot, which can be observed by scanning tunneling microscopy. Furthermore, the structure inversion asymmetry could also enlarge the helical topological superconductor state in the phase diagram, making the realization of such an exotic state more feasible. The electrical control of topological phases could further apply to van der Waals materials such as two-dimensional transition metal dichalcogenides.