Enhancement of Proximity Induced Superconductivity in a Planar Ge Hole Gas

TL;DR

This paper demonstrates high-quality, magnetic-field-resistant superconductor-graphene hybrid devices using aluminum and niobium contacts on germanium hole gases, enabling advanced quantum technology applications.

Contribution

It introduces a novel hybrid device with high transparency and robustness against magnetic fields, combining aluminum and niobium to enhance superconducting properties in germanium-based systems.

Findings

Devices withstand magnetic fields beyond 1.8 Tesla

High transparency and low disorder in JoFETs

Phase-biasing of individual JoFETs demonstrated

Abstract

Hole gases in planar germanium can have high mobilities in combination with strong spin-orbit interaction and electrically tunable g-factors, and are therefore emerging as a promising platform for creating hybrid superconductor-semiconductor devices. A key challenge towards hybrid Ge-based quantum technologies is the design of high-quality interfaces and superconducting contacts that are robust against magnetic fields. In this work, by combining the assets of aluminum, which provides good contact to the Ge, and niobium, which has a significant superconducting gap, we demonstrate highly transparent low-disordered JoFETs with relatively large \IcRn \ products that are capable of withstanding high magnetic fields. We furthermore demonstrate the ability of phase-biasing individual JoFETs, opening up an avenue to explore topological superconductivity in planar Ge. The persistence of superconductivity in the reported hybrid devices beyond 1.8 Tesla paves the way towards integrating spin qubits and proximity-induced superconductivity on the same chip.