Unveiling the Current-Phase Relationship of InSb Nanoflag Josephson Junctions Using a NanoSQUID Magnetometer

Planar Josephson junctions (JJs) based on InSb nanoflags have recently emerged as an intriguing platform in superconducting electronics. The knowledge of the current-phase relationship (CPR) of such hybrid junctions is crucial for their applications. This letter presents the fabrication and investigation of superconducting quantum interference devices (SQUIDs) employing InSb nanoflag JJs. The observed features are well reproduced through numerical simulations. By measuring interference patterns in both symmetric and asymmetric SQUID configurations, we extract unprecedented details of the junctions' CPRs. Our results demonstrate the skewness of the CPR, showing significant contributions from higher harmonics. We explore the magnetic field response of the devices across a wide range of fields (±30 mT). Finally, we assess the flux-to-voltage sensitivity of the SQUIDs to evaluate their performance as magnetometers, identifying a magnetic flux noise of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mrow><mml:mi>S</mml:mi></mml:mrow><mml:mrow><mml:mi>Φ</mml:mi></mml:mrow><mml:mrow><mml:mn>1</mml:mn><mml:mo>/</mml:mo><mml:mn>2</mml:mn></mml:mrow></mml:msubsup><mml:mo>=</mml:mo><mml:mn>4.4</mml:mn><mml:mo>×</mml:mo><mml:mn>1</mml:mn><mml:msup><mml:mrow><mml:mn>0</mml:mn></mml:mrow><mml:mrow><mml:mo>-</mml:mo><mml:mn>6</mml:mn></mml:mrow></mml:msup><mml:mo>⁡</mml:mo><mml:msub><mml:mrow><mml:mi>Φ</mml:mi></mml:mrow><mml:mrow><mml:mn>0</mml:mn></mml:mrow></mml:msub><mml:mo>/</mml:mo><mml:mi>√</mml:mi><mml:mi>H</mml:mi><mml:mi>z</mml:mi></mml:math>. These results showcase potential applications in nanoscale magnetometry.