Epitaxial Pb on InAs nanowires

Semiconductor-superconductor hybrids are widely used for realising complex quantum phenomena such as topological superconductivity and spins coupled to Cooper pairs. Accessing exotic regimes at high magnetic fields and increasing operating temperatures beyond the state-of-the-art requires new, epitaxially matched semiconductor-superconductor materials. The challenge is to generate favourable conditions for heterostructure formation between materials with the desired inherent properties. Here, we harness increased knowledge of metal-on-semiconductor growth to develop InAs nanowires with epitaxially matched, single crystal, atomically flat Pb films along the entire nanowire. These highly ordered heterostructures have a critical temperature of 7 K and a superconducting gap of 1.25 meV, which remains hard at 8.5 T, thereby more than doubling the available parameter space. Additionally, InAs/Pb island devics exhibit magnetic field-driven transitions from Cooper pair to single electron charging; a pre-requisite for use in topological quantum computation. Introducing semiconductor-Pb hybrids potentially enables access to entirely new regimes for an array of quantum systems.