# Hard superconducting gap in InSb nanowires

## TL;DR

This paper demonstrates how to achieve a hard superconducting gap in InSb nanowires by optimizing the interface with NbTiN, enabling stable topological superconductivity under magnetic fields for quantum computing applications.

## Contribution

It provides a systematic method to improve interface homogeneity and induce a hard superconducting gap in InSb nanowires, crucial for topological quantum computing.

## Key findings

- Achieved a hard superconducting gap in InSb nanowires.
- Maintained superconductivity under magnetic fields (~0.5 Tesla).
- Provided guidelines for inducing superconductivity in various platforms.

## Abstract

Topological superconductivity is a state of matter that can host Majorana modes, the building blocks of a topological quantum computer. Many experimental platforms predicted to show such a topological state rely on proximity-induced superconductivity. However, accessing the topological properties requires an induced hard superconducting gap, which is challenging to achieve for most material systems. We have systematically studied how the interface between an InSb semiconductor nanowire and a NbTiN superconductor affects the induced superconducting properties. Step by step, we improve the homogeneity of the interface while ensuring a barrier-free electrical contact to the superconductor, and obtain a hard gap in the InSb nanowire. The magnetic field stability of NbTiN allows the InSb nanowire to maintain a hard gap and a supercurrent in the presence of magnetic fields (~ 0.5 Tesla), a requirement for topological superconductivity in one-dimensional systems. Our study provides a guideline to induce superconductivity in various experimental platforms such as semiconductor nanowires, two dimensional electron gases and topological insulators, and holds relevance for topological superconductivity and quantum computation.