Nonlocality of Majorana bound states revealed by electron waiting times in a topological Andreev interferometer

TL;DR

This paper demonstrates that electron waiting times and their correlations in a topological Andreev interferometer reveal nonlocal Majorana bound states, offering a new method to detect topological superconductivity beyond traditional conductance measurements.

Contribution

It introduces a novel approach using electron waiting time analysis to identify nonlocal Majorana states in a topological superconducting setup, highlighting effects not observable through conductance alone.

Findings

Waiting times are sensitive to Majorana states but uncorrelated for all phase differences.

At phase difference π, hole waiting times show strong correlations.

Crossed hole-electron distributions exhibit unique behaviors due to Majorana nonlocality.

Abstract

The analysis of waiting times of electron transfers has recently become experimentally accessible owing to advances in noninvasive probes working in the short-time regime. We study electron waiting times in a topological Andreev interferometer: a superconducting loop with controllable phase difference connected to a quantum spin Hall edge, where the edge state helicity enables the transfer of electrons and holes into separate leads, with transmission controlled by the loop's phase difference $\phi$. This setup features gapless Majorana bound states at $\phi=\pi$. The waiting times for electron transfers across the junction are sensitive to the presence of the gapless states, but are uncorrelated for all $\phi$. By contrast, at $\phi=\pi$ the waiting times of Andreev-scattered holes show a strong correlation and the crossed (hole-electron) distributions feature a unique behavior. Both effects exclusively result from the nonlocal properties of Majorana bound states. Consequently, electron waiting times and their correlations could circumvent some of the challenges for detecting topological superconductivity and Majorana states beyond conductance signatures.