Probing electron-hole components of subgap states in Coulomb blockaded Majorana islands

TL;DR

This paper proposes a method using Coulomb-blockade conductance peak ratios to distinguish Majorana bound states from trivial Andreev bound states in nanowire systems, aiding in the identification of topological superconductivity.

Contribution

It introduces a novel approach to differentiate MBSs from ABSs by analyzing electron-hole components via conductance peak ratios in Coulomb blockade experiments.

Findings

Peak height ratios approach 0.5 for long wires with MBSs.

Ratios oscillate with Zeeman energy in short wires with overlapping MBSs.

Method can help experimentally distinguish topological from trivial states.

Abstract

Recent tunneling spectroscopy experiments in semiconducting nanowires with proximity-induced superconductivity have reported robust zero-bias conductance peaks. Such a feature can be compatible with the existence of topological Majorana bound states (MBSs) and with a trivial Andreev bound state (ABS) near zero energy. Here, we argue that additional information, that can distinguish between the two cases, can be extracted from Coulomb-blockade experiments of Majorana islands. The key is the ratio of peak heights of consecutive conductance peaks give information about the electron and hole components of the lowest-energy subgap state. In the MBS case, this ratio goes to one half for long wires, while for short wires with finite MBS overlap it oscillates a function of Zeeman energy with the same period as the MBS energy splitting. We explain how the additional information might help to distinguish a trivial ABS at zero energy from a true MBS and show case examples.