Parity-conserving Cooper-pair transport and ideal superconducting diode in planar Germanium
Marco ValentiniOliver SagiLevon BaghumyanThijs de GijselJason JungStefano CalcaterraAndrea BallabioJuan Aguilera ServinKushagra AggarwalMarian JanikThomas AdletzbergerRub\'en Seoane SoutoMartin LeijnseJeroen DanonConstantin Schrade
Marco ValentiniOliver SagiLevon Baghumyan
Superconductor/semiconductor hybrid devices have attracted increasing interest in the past years. Superconducting electronics aims to complement semiconductor technology, while hybrid architectures are at the forefront of new ideas such as topological superconductivity and protected qubits. In this work, we engineer the induced superconductivity in two-dimensional germanium hole gas by varying the distance between the quantum well and the aluminum. We demonstrate a hard superconducting gap and realize an electrically and flux tunable superconducting diode using a superconducting quantum interference device (SQUID). This allows to tune the current phase relation (CPR), to a regime where single Cooper pair tunneling is suppressed, creating a $\sin \left( 2 \varphi \right)$ CPR. Shapiro experiments complement this interpretation and the microwave drive allows to create a diode with 100% efficiency. The reported results open up the path towards integration of spin qubit devices, microwave resonators and (protected) superconducting qubits on a silicon technology compatible platform.