Microscopic origin of the magnetically active domains in InAs/Al nanowire Josephson junctions

Determine unambiguously the microscopic origin of the magnetically active domains responsible for the Barkhausen-like switching-current jumps observed in n-doped InAs/Al nanowire Josephson junctions, distinguishing among mechanisms such as collective reconfigurations of surface magnetic moments and correlated magnetic impurities in the hybrid nanowire environment.

Background

The paper reports discrete switching-current jumps at low perpendicular magnetic fields (about ±3 mT) in n-doped InAs/Al nanowire Josephson junctions, consistent with Barkhausen-like avalanche switching between metastable magnetic configurations coupled to the weak link.

The jump field is essentially temperature independent from 30 to 900 mK, while the superconducting critical field follows the temperature dependence of thin Al films. The authors model the behavior using an effective-field picture where local magnetization contributes an intrinsic field offset that shifts and distorts a Fraunhofer-like interference pattern.

Although the data point to intrinsic magnetic reconfigurations (rather than flux trapping or Zeeman-driven 0–π transitions), the precise microscopic origin of the magnetically active domains remains unresolved. Prior work suggests possibilities including localized magnetic moments and surface-related magnetism in similar nanowire systems.