Evidence of topological superconductivity in planar Josephson junctions

TL;DR

This study provides experimental evidence of phase-tuned topological superconductivity in planar Josephson junctions, showing zero-bias conductance peaks consistent with Majorana zero modes, which are promising for quantum computing applications.

Contribution

First demonstration of phase-dependent zero-bias peaks indicating topological superconductivity in planar Josephson junctions on InAs/Al heterostructures.

Findings

Zero-bias conductance peaks depend on phase difference {} in Josephson junctions.

Phase tuning reduces the magnetic field needed for zero-bias peaks.

Results align with models of Majorana zero modes in finite-size junctions.

Abstract

Majorana zero modes are quasiparticle states localized at the boundaries of topological superconductors that are expected to be ideal building blocks for fault-tolerant quantum computing. Several observations of zero-bias conductance peaks measured in tunneling spectroscopy above a critical magnetic field have been reported as experimental indications of Majorana zero modes in superconductor/semiconductor nanowires. On the other hand, two dimensional systems offer the alternative approach to confine Ma jorana channels within planar Josephson junctions, in which the phase difference {\phi} between the superconducting leads represents an additional tuning knob predicted to drive the system into the topological phase at lower magnetic fields. Here, we report the observation of phase-dependent zero-bias conductance peaks measured by tunneling spectroscopy at the end of Josephson junctions realized on a InAs/Al heterostructure. Biasing the junction to {\phi} ~ {\pi} significantly reduces the critical field at which the zero-bias peak appears, with respect to {\phi} = 0. The phase and magnetic field dependence of the zero-energy states is consistent with a model of Majorana zero modes in finite-size Josephson junctions. Besides providing experimental evidence of phase-tuned topological superconductivity, our devices are compatible with superconducting quantum electrodynamics architectures and scalable to complex geometries needed for topological quantum computing.