Quantum dot spectroscopy of proximity-induced superconductivity in a two-dimensional electron gas

TL;DR

This paper demonstrates a hybrid superconductor-quantum dot device in a 2D electron gas, revealing the proximity-induced energy gap through cotunneling spectroscopy, advancing understanding of superconductivity in low-dimensional systems.

Contribution

It introduces a novel top-down nanofabrication method to create superconductor-quantum dot devices in a 2D electron gas, enabling direct spectroscopic probing of proximity effects.

Findings

Proximity-induced energy gap observed in a ballistic 2D electron gas.

Quantum dot defined by electrostatic gates within a superconductor-normal junction.

Spectroscopy reveals strong Coulomb blockade and cotunneling effects.

Abstract

We report the realization of a hybrid superconductor-quantum dot device by means of top-down nanofabrication starting from a two dimensional electron gas in a InGaAs/InAlAs semiconductor heterostructure. The quantum dot is defined by electrostatic gates placed within the normal region of a planar Nb-InGaAs quantum well-Nb junction. Measurements in the regime of strong Coulomb blockade as well as cotunneling spectroscopy allow to directly probe the proximity-induced energy gap in a ballistic two-dimensional electron gas coupled to superconductors.