Stefan Heun

Superconducting Quantum Interference Devices based on InSb nanoflag Josephson junctions

  1. Andrea Chieppa,
  2. Gaurav Shukla,
  3. Simone Traverso,
  4. Giada Bucci,
  5. Valentina Zannier,
  6. Samuele Fracassi,
  7. Niccolo Traverso Ziani,
  8. Maura Sassetti,
  9. Matteo Carrega,
  10. Fabio Beltram,
  11. Francesco Giazotto,
  12. Lucia Sorba,
  13. and Stefan Heun
Planar Josephson junctions (JJs) based on InSb nanoflags have recently emerged as an intriguing platform in superconducting electronics. This letter presents the fabrication and investigation
of superconducting quantum interference devices (SQUIDs) employing InSb nanoflag JJs. We provide measurements of 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 JJs, demonstrating significant contributions from higher harmonics. We explore the magnetic field response of the devices across a wide range of fields (±30 mT), up to the single-junction interference regime, where a Fraunhofer-like pattern is detected. Finally, we assess the flux-to-voltage sensitivity of the SQUIDs to evaluate their performance as magnetometers. A magnetic flux noise of S1/2Φ=4.4×10−6Φ0/Hz‾‾‾√ is identified, indicating potential applications in nanoscale magnetometry.
arxiv pdf

Evidence of Josephson coupling in a few-layer black phosphorus planar Josephson junction

  1. Francesca Telesio,
  2. Matteo Carrega,
  3. Giulio Cappelli,
  4. Andrea Iorio,
  5. Alessandro Crippa,
  6. Elia Strambini,
  7. Francesco Giazotto,
  8. Manuel Serrano-Ruiz,
  9. Maurizio Peruzzini,
  10. and Stefan Heun
Setting up strong Josephson coupling in van der Waals materials in close proximity to superconductors offers several opportunities both to inspect fundamental physics and to develop
novel cryogenic quantum technologies. Here we show evidence of Josephson coupling in a planar few-layer black Phosphorus junction. The planar geometry allows us to probe the junction behavior by means of external gates, at different carrier concentrations. Clear signatures of Josephson coupling are demonstrated by measuring supercurrent flow through the junction at milli Kelvin temperatures. Manifestation of Fraunhofer pattern with a transverse magnetic field is also reported, confirming the Josephson coupling. These findings represent the first evidence of proximity Josephson coupling in a planar junction based on a van der Waals material beyond graphene and open the way to new studies, exploiting the peculiar properties of exfoliated black phosphorus thin flakes.
arxiv pdf