Quantized conductance doubling and hard gap in a two-dimensional semiconductor-superconductor heterostructure

TL;DR

This paper demonstrates a 2D semiconductor-superconductor heterostructure with a hard superconducting gap and quantized conductance doubling, paving the way for scalable topological quantum devices.

Contribution

It reports the fabrication of a pristine, gateable 2D heterostructure with epitaxial Al, achieving a hard gap and quantized conductance, advancing topological quantum computing research.

Findings

Hard superconducting gap observed in tunneling regime.

Quantized conductance plateau at 4e^2/h in open regime.

Atomically pristine interfaces enabling scalable device fabrication.

Abstract

The prospect of coupling a two-dimensional (2D) semiconductor heterostructure to a superconductor opens new research and technology opportunities, including fundamental problems in mesoscopic superconductivity, scalable superconducting electronics, and new topological states of matter. For instance, one route toward realizing topological matter is by coupling a 2D electron gas (2DEG) with strong spin-orbit interaction to an s-wave superconductor. Previous efforts along these lines have been hindered by interface disorder and unstable gating. Here, we report measurements on a gateable InGaAs/InAs 2DEG with patterned epitaxial Al, yielding multilayer devices with atomically pristine interfaces between semiconductor and superconductor. Using surface gates to form a quantum point contact (QPC), we find a hard superconducting gap in the tunneling regime, overcoming the soft-gap problem in 2D superconductor-semiconductor hybrid systems. With the QPC in the open regime, we observe a first conductance plateau at 4e^2/h, as expected theoretically for a normal-QPC-superconductor structure. The realization of a hard-gap semiconductor-superconductor system that is amenable to top-down processing provides a means of fabricating scalable multicomponent hybrid systems for applications in low-dissipation electronics and topological quantum information.