From nonreciprocal to charge-4e supercurrents in Ge-based Josephson devices with tunable harmonic content

Abstract

Hybrid superconductor(S)-semiconductor(Sm) devices bring a range of new functionalities into superconducting circuits. In particular, hybrid parity-protected qubits and Josephson diodes were recently proposed and experimentally demonstrated. Such devices leverage the non-sinusoidal 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 $\pi$-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 novel superconducting quantum circuits.

8 pages, 5 figures

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Cited by in corpus (10)

• Gatemon qubit on a germanium quantum-well heterostructure
• The hybrid Josephson rhombus: A superconducting element with tailored current-phase relation
• Voltage-controlled synthesis of higher harmonics in hybrid Josephson junction circuits
• Tunable superconducting diode effect in higher-harmonic InSb nanosheet interferometers
• Thermomodulated intrinsic Josephson effect in Kagome CsV3Sb5
• Superconducting Proximity Effect in Two-Dimensional Hole Gases
• Effect of 2${}^{\text{nd}}$ harmonic current--phase relation on a behavior of a Josephson Traveling Wave Parametric Amplifier
• Diode effect in Shapiro steps in an asymmetric SQUID with a superconducting nanobridge
• Tunable diode effect in a superconducting tunnel junction with biharmonic drive
• Gate- and flux-tunable sin(2$\phi$) Josephson element with proximitized Ge-based junctions