Abstract

High-quality III-V narrow bandgap semiconductor materials with strong spin-orbit coupling and large Lande g-factor provide a promising platform for next-generation applications in the field of high-speed electronics, spintronics, and quantum computing. InSb stands out due to its narrow bandgap, high carrier mobility, and small effective mass, making it very appealing for these applications. In fact, this material has attracted tremendous attention in recent years for the implementation of topological superconducting states.
In this context, the simultaneous breaking of time-reversal and inversion symmetry can lead to peculiar effects in Josephson junctions, such as the anomalous Josephson effect or supercurrent rectification, which is a dissipationless analog of the diode effect. Due to their potential impact in new quantum technologies, it is important to find robust platforms and external means to manipulate the above effects in a controlled way. We demonstrate that hybrid Josephson junctions made of high-quality InSb nanoflags [1] constitute a promising platform for supercurrent rectification due to its strong spin orbit coupling. The high quality of the devices enabled the observation of the diode effect in these Josephson junctions [2]. When subjected to an in-plane magnetic field, the devices enter a non-reciprocal transport regime, manifesting an asymmetry between positive and negative critical currents.
Furthermore, we fabricated and investigated superconducting quantum interference devices (SQUIDs) based on InSb nanoflag Josephson junctions [3]. We measured interference patterns in both symmetric and asymmetric geometries. The interference patterns in both configurations can be modulated by a back-gate voltage, a feature well reproduced through numerical simulations. The observed behavior aligns with the skewed current-phase relations of the Josephson junctions, demonstrating significant contributions from higher harmonics. Finally, we assess the flux-to-voltage sensitivity of the SQUIDs to evaluate their performance as magnetometers.

Acknowledgments

We acknowledge support from project PRIN2022 2022-PH852L(PE3) TopoFlags-“Non-reciprocal supercurrent and topological transition in hybrid Nb-InSb nanoflags” funded by the European Community-Next Generation EU within the program “PNRR Missione 4- Componente 2-Investimento 1.1 Fondo per il Programma Nazionale di Ricerca e Progetti di Rilevante Interesse Nazionale (PRIN)” and by PNRR MUR Project No. PE0000023-NQSTI.

References

1. S. Salimian et al., Appl. Phys. Lett. 119 (2021) 214004.
2. B. Turini et al., Nano Lett. 22 (2022) 8502.
3. A. Chieppa et al., Nano Lett. 25 (2025) 14412.