Distinguishing Majorana bound states from localized Andreev bound states by interferometry

TL;DR

This paper proposes an interferometry experiment to distinguish Majorana bound states from Andreev bound states in superconducting nanostructures, based on their different effects on conductance oscillations in a Coulomb-blockaded island.

Contribution

It introduces a novel interferometry method that can differentiate MBSs from ABSs by analyzing flux-dependent conductance oscillations in a ring setup.

Findings

Interference suppression occurs with ABSs when the ground state is nearly degenerate.

MBSs cause $h / e$-periodic conductance oscillations due to nondegenerate ground state.

The method can be implemented with semiconducting nanowires or 2D electron gases.

Abstract

Experimental evidence for Majorana bound states (MBSs) is so far mainly based on the robustness of a zero-bias conductance peak. However, similar features can also arise due to Andreev bound states (ABSs) localized at the end of an island. We show that these two scenarios can be distinguished by an interferometry experiment based on embedding a Coulomb-blockaded island into an Aharonov-Bohm ring. For two ABSs, when the ground state is nearly degenerate, cotunneling can change the state of the island and interference is suppressed. By contrast, for two MBSs the ground state is nondegenerate and cotunneling has to preserve the island state, which leads to $h / e$-periodic conductance oscillations with magnetic flux. Such interference setups can be realized with semiconducting nanowires or two-dimensional electron gases with proximity-induced superconductivity and may also be a useful spectroscopic tool for parity-flip mechanisms.