Detecting Majorana nonlocality using strongly coupled Majorana bound states

TL;DR

This paper proposes methods to detect Majorana nonlocality through Coulomb-mediated coupling in quantum spin Hall systems, using flux periodicity measurements to distinguish Majorana states from trivial states.

Contribution

It introduces a falsifiable detection strategy for Majorana nonlocality leveraging Coulomb coupling and flux periodicity, applicable without opening a magnetic gap in helical edge states.

Findings

Long-range MBS coupling shows $h/e$ flux periodicity in conductance and supercurrent.

Switching off charging energy restores $h/2e$ periodicity, confirming Majorana origin.

Proposed setup enables detection of Majorana nonlocality without magnetic gap opening.

Abstract

Majorana bound states (MBS) differ from the regular zero energy Andreev bound states in their nonlocal properties, since two MBS form a single fermion. We design strategies for detection of this nonlocality by using the phenomenon of Coulomb-mediated Majorana coupling in a simplest setting which still retains falsifiability. Focusing on the implementation of MBS based on the quantum spin Hall effect, we also design a way to probe Majoranas without the need to open a magnetic gap in the helical edge states. In the setup that we analyse, long range MBS coupling manifests in the $h/e$ magnetic flux periodicity of tunneling conductance and supercurrent. While $h/e$ is also the periodicity of Aharonov-Bohm effect and persistent current, we show how to ensure its Majorana origin by verifying that switching off the charging energy restores $h/2e$ periodicity conventional for superconducting systems.