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Magnetically Induced Switching-Current Jumps in InAs/Al Josephson Junctions

Ofelia Durante, Roberta Citro, Elia Strambini, Valeria Demontis, Mirko Rocci, Alessandro Braggio, Sergio Battiato, Valentina Zannier, Lucia Sorba, Francesco Giazotto, Claudio Guarcello

Abstract

We report Barkhausen-like switching at millitesla fields in an $n$-doped InAs/Al nanowire Josephson junction, which serves as an interferometric probe of intrinsic magnetic reconfigurations, as evidenced by discrete switching-current jumps. At $T=30$~mK the device displays a Fraunhofer-like modulation with $I_{\mathrm{sw}}(0)\approx 0.24~μ\mathrm{A}$ and an abrupt transition at $|B|\approx 3~\mathrm{mT}$ between two branches differing by $ΔI_{\mathrm{sw}}\approx 0.13~μ\mathrm{A}$. By tracking the characteristic field scales from $30$ to $900$~mK, we find that the jump field is essentially temperature-independent, whereas the superconducting critical field decreases with temperature, as expected for thin Al films. The sharp discontinuity, sweep-direction asymmetry, and reproducibility across repeated scans point to avalanche-like switching between metastable magnetic configurations of the local magnetic texture, which are directly coupled to the weak link. Within an effective-field framework, each reconfiguration modifies a local field offset, thereby reshaping the interference response and leading to an abrupt reorganization of the switching-current pattern.

Magnetically Induced Switching-Current Jumps in InAs/Al Josephson Junctions

Abstract

We report Barkhausen-like switching at millitesla fields in an -doped InAs/Al nanowire Josephson junction, which serves as an interferometric probe of intrinsic magnetic reconfigurations, as evidenced by discrete switching-current jumps. At ~mK the device displays a Fraunhofer-like modulation with and an abrupt transition at between two branches differing by . By tracking the characteristic field scales from to ~mK, we find that the jump field is essentially temperature-independent, whereas the superconducting critical field decreases with temperature, as expected for thin Al films. The sharp discontinuity, sweep-direction asymmetry, and reproducibility across repeated scans point to avalanche-like switching between metastable magnetic configurations of the local magnetic texture, which are directly coupled to the weak link. Within an effective-field framework, each reconfiguration modifies a local field offset, thereby reshaping the interference response and leading to an abrupt reorganization of the switching-current pattern.

Paper Structure

This paper contains 10 sections, 22 equations, 9 figures.

Table of Contents

  1. Acknowledgments
  2. Data Availability Statement
  3. Notes
  4. S1: Additional switching current patterns of different samples
  5. S2: Flux-focusing estimate from electrode geometry
  6. S3: Wide- and Narrow-Junction Limits
  7. Wide junction, $W\gg\xi_H$ Cuevas2007PRL:
  8. Narrow junction, $W\ll\xi_H$ Montambaux2007ArXiv:
  9. S4: Minimal random-field Ising model for discrete magnetic reconfigurations
  10. S5: Excluding a Zeeman $0$--$\pi$ transition of the short junction

Figures (9)

  • Figure 1: Device and basic characterization. (a) Schematic of the InAs/Al NW JJ and four-wire current-bias measurement setup. (b) False-colour SEM of the junction area showing the InAs NW contacted by two superconducting Al leads; interelectrode spacing $L\simeq70$ nm. (c) $V$--$I$ characteristic at $T=30$ mK showing a switching current $I_{\mathrm{sw}}\approx 0.25~\mu$A and hysteresis upon retrapping.
  • Figure 2: Interference pattern and switching-current jump. (a) Differential resistance map $dV/dI(I,B)$ at $T=30$ mK. The dark region corresponds to the superconducting branch; the bright boundary marks $I_{\mathrm{sw}}(B)$. (b) Switching current $I_{\mathrm{sw}}(B)$ at different temperatures (30--900 mK), showing a Fraunhofer-like modulation and an abrupt transition at $|B|\approx3$ mT between two branches. The inset shows a cartoon of the InAs NW, between two superconducting Al leads, which is represented as a sequence of magnetic domains (blue/red), with out-of-plane magnetization oriented either up or down (arrows).
  • Figure 3: Temperature dependence of superconducting and jump field scales. (a) Positive and negative critical fields $B_c^\pm$ versus temperature; dotted lines are parabolic fits. (b) Jump fields $B_j^\pm$ versus temperature, remaining nearly constant around $\pm3$ mT. (c) Jump amplitude $\Delta I_{\mathrm{sw}}(B_j^\pm)$ versus temperature.
  • Figure 4: Sweep-direction hysteresis and additional discrete switches. Differential resistance maps $dV/dI(I,B)$ at $T=30$ mK for (a) a sweep from $B=0$ to $-15$ mT and (b) a sweep from $-15$ mT to $0$. Beyond the main switch near $|B|\simeq3$ mT, smaller discontinuities depend on sweep history, consistent with metastable magnetic switching.
  • Figure S1: Additional switching-current patterns across devices.$I_{\rm sw}(B)$ for three InAs-NW JJs: (a) D3-d5 at $T = 30$ mK, (b) C2-d1 at $T = 700$ mK, and (c) C2-d5 at $T = 30$ mK. Data acquired with the magnetic field swept from negative to positive (see the arrow).
  • ...and 4 more figures