16th International Conference on Muon Spin Rotation, Relaxation and Resonance (μSR2025)

Nanoscale Measurement of Superconducting Nb’s Intrinsic Length Scales Using Low-Energy μSR

Not scheduled

20m

Poster Presentation Superconductivity Poster Session 1

Speaker

Dr Ryan McFadden (TRIUMF Inc.)

Description

A superconductor’s intrinsic length scales – the London penetration depth λ_L and Bardeen-Cooper-Schrieffer (BCS) coherence length ξ₀ – are closely connected to its electronic structure and govern salient features such at its Meissner response. Leveraging recent advances in the preparation [1] and characterization [2] of Nb metal for technical applications (e.g., superconducting radiofrequency accelerator cavities), we quantify the elemental superconductor's λ_L and ξ₀ from depth-resolved measurements of its Meissner profile using low-energy muon spin spectroscopy (μSR). Accounting for known systematics [3] and subtleties [4] in the measurements, we find values for the lengths that are ~10 nm shorter than those nominally quoted for the metal (see, e.g., [5]), but in good agreement with predictions from electronic structure calculations and compatible with independent measurements of Nb's mass-enhancement factor Z. Using our results, we comment on the recently proposed type-I superconductivity of pure Nb [6].

References

1. S. Posen et al., Phys. Rev. Appl. 13, 014024 (2020).
2. J. W. Angle et al., J. Vac. Sci. Technol. B 40, 024003 (2022).
3. R. M. L. McFadden et al., Phys. Rev. Appl. 19, 044018 (2023).
4. R. M. L. McFadden et al., Appl. Phys. Lett. 124, 086101 (2024).
5. B. W. Maxfield et al., Phys. Rev. 139, A1515 (1965).
6. R. Prozorov et al., Phys. Rev. B 106, L180505 (2022).