Majorana bound states in encapsulated bilayer graphene

TL;DR

This paper proposes a 2D platform using encapsulated bilayer graphene with induced spin-orbit coupling to realize Majorana bound states under weaker magnetic fields, offering a promising route for topological quantum computing.

Contribution

It introduces a novel 2D approach with encapsulated bilayer graphene that enables Majorana states without strong magnetic fields or interactions, expanding experimental possibilities.

Findings

Majorana bound states can be stabilized at sample corners.

The phase diagram shows a topological phase accessible with current technology.

Majorana states exhibit a 4π-periodic Josephson effect.

Abstract

The search for robust topological superconductivity and Majorana bound states continues, exploring both one-dimensional (1D) systems such as semiconducting nanowires and two-dimensional (2D) platforms. In this work we study a 2D approach based on graphene bilayers encapsulated in transition metal dichalcogenides that, unlike previous proposals involving the Quantum Hall regime in graphene, requires weaker magnetic fields and does not rely on interactions. The encapsulation induces strong spin-orbit coupling on the graphene bilayer, which opens a sizeable gap and stabilizes fragile pairs of helical edge states. We show that, when subject to an in-plane Zeeman field, armchair edges can be transformed into p-wave one-dimensional topological superconductors by contacting them laterally with conventional superconductors. We demonstrate the emergence of Majorana bound states (MBSs) at the sample corners of crystallographically perfect flakes, belonging either to the D or the BDI symmetry classes depending on parameters. We compute the phase diagram, the resilience of MBSs against imperfections, and their manifestation as a 4$\pi$-periodic effect in Josephson junction geometries, all suggesting the existence of a topological phase within experimental reach.