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<p>Abrikosov vortices in type-II superconductors influence current flow, dissipation and coherence, thereby limiting superconducting quantum technologies. In mesoscopic circuit elements, the entry and pinning of a single vortex can shift resonant frequencies, redistribute flux and degrade device performance. Here, we use a flux-mediated cavity-optomechanical platform, in which a suspended superconducting aluminum nanostring forms one arm of a SQUID terminating a microwave resonator, to investigate vortex-entry processes through nanomechanical elastic signatures. Operating at <i>T</i>&#xa0;≈&#xa0;85 mK with 0.25 mT in-plane-field resolution, we resolve discrete jumps of the mechanical resonance frequency consistent with the stochastic entry of one or a few singly quantized Abrikosov vortices. Their field positions vary between thermal cycles, indicating disorder-mediated nucleation through a quenched pinning landscape. These events are superimposed on a smooth power-law stiffening background identified with the collective Campbell–Labusch elastic response. Recasting the jumps as equivalent force signatures yields attonewton-scale forces and, within a single-event pinning model, characteristic vortex-pinning energies of 0.09&#xa0;−&#xa0;0.44 eV. The smooth background gives a collective Labusch parameter of order 10<sup>14</sup> N m<sup>−4</sup>. Our results establish cavity-optomechanical sensing as an in situ probe of vortex matter and identify vortex entry as a quantitative design constraint for flux-mediated superconducting quantum circuits.</p>

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Resolving Abrikosov vortex entry in superconducting nanostring resonators via displacement-noise spectroscopy in cavity optomechanics

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年7月18日

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  • Thomas Luschmann,
  • Tahereh Sadat Parvini,
  • Lukas Niekamp,
  • Achim Marx,
  • Rudolf Gross,
  • Hans Huebl

摘要

Abrikosov vortices in type-II superconductors influence current flow, dissipation and coherence, thereby limiting superconducting quantum technologies. In mesoscopic circuit elements, the entry and pinning of a single vortex can shift resonant frequencies, redistribute flux and degrade device performance. Here, we use a flux-mediated cavity-optomechanical platform, in which a suspended superconducting aluminum nanostring forms one arm of a SQUID terminating a microwave resonator, to investigate vortex-entry processes through nanomechanical elastic signatures. Operating at T ≈ 85 mK with 0.25 mT in-plane-field resolution, we resolve discrete jumps of the mechanical resonance frequency consistent with the stochastic entry of one or a few singly quantized Abrikosov vortices. Their field positions vary between thermal cycles, indicating disorder-mediated nucleation through a quenched pinning landscape. These events are superimposed on a smooth power-law stiffening background identified with the collective Campbell–Labusch elastic response. Recasting the jumps as equivalent force signatures yields attonewton-scale forces and, within a single-event pinning model, characteristic vortex-pinning energies of 0.09 − 0.44 eV. The smooth background gives a collective Labusch parameter of order 1014 N m−4. Our results establish cavity-optomechanical sensing as an in situ probe of vortex matter and identify vortex entry as a quantitative design constraint for flux-mediated superconducting quantum circuits.