Local and Nonlocal Transport Spectroscopy in Planar Josephson Junctions

TL;DR

This study uses local and nonlocal transport spectroscopy in a phase-biased planar Josephson junction to identify topological phase transitions and zero-bias conductance peaks, advancing understanding of topological superconductivity.

Contribution

It provides the first simultaneous measurement of local and nonlocal conductances in a planar Josephson junction, revealing signatures of topological transitions and ZBCPs.

Findings

Gap closing and reopening observed in spectra.

Strong end-to-end correlation of gap reopening.

Weak correlation of local zero-bias conductance peaks.

Abstract

We report simultaneously acquired local and nonlocal transport spectroscopy in a phase-biased planar Josephson junction based on an epitaxial InAs/Al hybrid two-dimensional heterostructure. Quantum point contacts at the junction ends allow measurement of the 2 x 2 matrix of local and nonlocal tunneling conductances as a function of magnetic field along the junction, phase difference across the junction, and carrier density. A closing and reopening of a gap was observed in both the local and nonlocal tunneling spectra as a function of magnetic field. For particular tunings of junction density, gap reopenings were accompanied by zero-bias conductance peaks (ZBCPs) in local conductances. End-to-end correlation of gap reopening was strong, while correlation of local ZBCPs was weak. A simple, disorder-free model of the device shows comparable conductance matrix behavior associated with a topological phase transition. Phase dependence helps distinguish possible origins of the ZBCPs.