Probing electron-hole weights of an Andreev bound state by transient currents

TL;DR

This paper introduces a method to measure the electron-hole composition of Andreev bound states using transient currents, enabling identification of Majorana bound states in superconducting systems.

Contribution

It proposes a novel tunneling measurement protocol to determine electron-hole weights and extract ABS energy levels from transient current spectra.

Findings

The protocol can distinguish between ABSs, quasi-MBSs, and MBSs based on electron-hole weights.

Numerical simulations demonstrate the method's effectiveness in a 1D Majorana nanowire model.

The approach enables detection of zero-energy MBSs with equal electron-hole weights.

Abstract

Andreev bound states (ABSs) are localized quantum states that contain both electron and hole components. They ubiquitously reside in inhomogeneous superconducting systems. Following theoretical analysis, we propose to probe the electron-hole weights of an ABS via a local tunneling measurement that detects the transient current under a steplike pulse bias. With our protocol, the ABS energy level can also be obtained from peaks of the Fourier spectrum of the transient current. Our protocol can be applied to detect robust zero-energy Majorana bound states (MBSs), which have equal electron-hole weights, in candidate platforms where local tunneling spectroscopy measurement is possible. In the 1D Majorana nanowire model, we numerically calculate the electron-hole weights for different types of low-energy bound states, including ABSs, quasi-MBSs, and MBSs.