Tunable superconducting diode effect in higher-harmonic InSb nanosheet interferometers

TL;DR

This paper demonstrates a tunable superconducting diode effect in InSb nanosheet-based SQUIDs, where the diode polarity and efficiency can be controlled via gate voltage, magnetic flux, and microwave power, revealing higher harmonic contributions.

Contribution

It introduces a gate- and flux-tunable superconducting diode in InSb nanosheet SQUIDs with controllable polarity and efficiency, highlighting the role of higher harmonics in the current-phase relation.

Findings

Diode effect can be tuned by gate voltage and magnetic flux.

Higher harmonics significantly influence the diode effect.

Microwave power can switch the diode polarity.

Abstract

Superconducting diodes, characterized by the nonreciprocal supercurrent flow, have gained significant attention for their potential in dissipationless electronics. This study presents a superconducting quantum interference device (SQUID) composed of two Al-InSb nanosheet Josephson junctions. Utilizing prepatterned local backgates, we achieve a gate- and flux-tunable superconducting diode with controllable efficiency in both amplitude and sign. Numerical simulations attribute the diode effect to higher harmonics in the current-phase relation. Crucially, fractional Shapiro step experiments provide direct insights into the evolution of these higher harmonics with flux tuning, showcasing significant enhancements in the second-harmonic signatures of the SQUID near half-integer flux quanta. Furthermore, we investigate the microwave-assisted diode response and experimentally show that the polarity of the diode effect can be switched by the microwave power. These results demonstrate the potential of InSb nanosheet-based hybrid devices as highly tunable elements for use in dissipationless electronics.