From nonreciprocal to charge-4e supercurrent in Ge-based Josephson devices with tunable harmonic content
Axel Leblanc, Chotivut Tangchingchai, Zahra Sadre Momtaz, Elyjah Kiyooka, Jean-Michel Hartmann, Gonzalo Troncoso Fernandez-Bada, Zoltán Scherübl, Boris Brun, Vivien Schmitt, Simon Zihlmann, Romain Maurand, Étienne Dumur, Silvano De Franceschi, François Lefloch
DOI 10.1103/PhysRevResearch.6.033281 · Physical Review Research
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Abstract
Hybrid superconductor(S)-semiconductor(Sm) devices bring a range of functionalities into superconducting circuits. In particular, hybrid parity-protected qubits and Josephson diodes were recently proposed and experimentally demonstrated. Such devices leverage the nonsinusoidal character of the Josephson current-phase relation (CPR) in highly transparent S-Sm-S junctions. Here, we report an experimental study of superconducting quantum-interference devices (SQUIDs) embedding Josephson field-effect transistors fabricated from a SiGe/Ge/SiGe heterostructure grown on a 200-mm silicon wafer. The single-junction CPR shows up to three harmonics with gate-tunable amplitude. In the presence of microwave irradiation, the ratio of the first two dominant harmonics, corresponding to single and double Cooper-pair transport processes, is consistently reflected in relative weight of integer and half-integer Shapiro steps. A combination of magnetic-flux and gate-voltage control enables tuning the SQUID functionality from a nonreciprocal Josephson-diode regime with 27% asymmetry to a π-periodic Josephson regime suitable for the implementation of parity-protected superconducting qubits. These results illustrate the potential of Ge-based hybrid devices as versatile and scalable building blocks of superconducting quantum circuits.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| Al Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 1.54 | Pressure not reported | unknown |
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