Ballistic superconductivity in semiconductor nanowires

TL;DR

This paper demonstrates ballistic superconductivity in high-quality InSb nanowires with NbTiN, enabling potential disorder-free Majorana devices by achieving quantized conductance, enhanced Andreev reflection, and a hard superconducting gap.

Contribution

It reports the realization of ballistic superconductivity in InSb nanowires with a high-quality superconductor interface, advancing the development of topological quantum devices.

Findings

Quantized conductance observed for normal carriers

Enhanced conductance for Andreev-reflecting carriers

Induced hard superconducting gap with reduced density of states

Abstract

Semiconductor nanowires have opened new research avenues in quantum transport owing to their confined geometry and electrostatic tunability. They have offered an exceptional testbed for superconductivity, leading to the realization of hybrid systems combining the macroscopic quantum properties of superconductors with the possibility to control charges down to a single electron. These advances brought semiconductor nanowires to the forefront of efforts to realize topological superconductivity and Majorana modes. A prime challenge to benefit from the topological properties of Majoranas is to reduce the disorder in hybrid nanowire devices. Here, we show ballistic superconductivity in InSb semiconductor nanowires. Our structural and chemical analyses demonstrate a high-quality interface between the nanowire and a NbTiN superconductor which enables ballistic transport. This is manifested by a quantized conductance for normal carriers, a strongly enhanced conductance for Andreev-reflecting carriers, and an induced hard gap with a significantly reduced density of states. These results pave the way for disorder-free Majorana devices.