A quantum dot in germanium proximitized by a superconductor
Lazar Lakic (University of Copenhagen)
William I.L. Lawrie (University of Copenhagen)
David van Driel (Kavli institute of nanoscience Delft, TU Delft - QRD/Kouwenhoven Lab, TU Delft - QuTech Advanced Research Centre)
Lucas E.A. Stehouwer (Kavli institute of nanoscience Delft, TU Delft - QuTech Advanced Research Centre, TU Delft - QCD/Scappucci Lab)
Yao Su (University of Copenhagen)
Menno Veldhorst (TU Delft - QN/Veldhorst Lab, TU Delft - QuTech Advanced Research Centre, Kavli institute of nanoscience Delft)
Giordano Scappucci (TU Delft - QCD/Scappucci Lab, TU Delft - QuTech Advanced Research Centre, Kavli institute of nanoscience Delft)
Ferdinand Kuemmeth (Universität Regensburg, University of Copenhagen)
Anasua Chatterjee (University of Copenhagen, Kavli institute of nanoscience Delft, TU Delft - QuTech Advanced Research Centre, TU Delft - QRD/Chatterjee Lab, TU Delft - QN/Chatterjee Lab)
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Abstract
As one of the few group IV materials with the potential to host superconductor–semiconductor hybrid devices, planar germanium hosting proximitized quantum dots is a compelling platform to achieve and combine topological superconductivity with existing and new qubit modalities. We demonstrate a quantum dot in a Ge/SiGe heterostructure proximitized by a platinum germanosilicide (PtSiGe) superconducting lead, forming a superconducting lead–quantum dot–superconducting lead junction. We show tunability of the coupling strength between the quantum dot and the superconducting lead, and gate control of the ratio of charging energy and the induced gap, and we tune the ground state of the system between even and odd parity. Furthermore, we characterize critical magnetic field strengths, finding a critical out-of-plane field of 0.90 ± 0.04 T. Finally, we explore sub-gap spin splitting, observing rich physics in the resulting spectra, that we model using a zero-bandwidth model in the Yu–Shiba–Rusinov limit. Our findings open up the physics of alternative spin and superconducting qubits, and the physics of Josephson junction arrays, in germanium.
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