Niobium's intrinsic coherence length and penetration depth revisited using low-energy muon spin spectroscopy and secondary-ion mass spectrometry
Ryan M. L. McFadden, Jonathan W. Angle, Eric M. Lechner, Michael J. Kelley, Charles E. Reece, Matthew A. Coble, Thomas Prokscha, Zaher Salman, Andreas Suter, Tobias Junginger
DOI 10.1103/2nsw-n8gf · Physical Review B
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Abstract
We report direct, simultaneous measurements of the London penetration depth (λL) and Bardeen-Cooper-Schrieffer coherence length (ξ0) in oxygen-doped niobium, with impurity concentrations spanning the “clean” to “dirty” limits. Two depth-resolved techniques—low-energy muon spin spectroscopy and secondary-ion mass spectrometry—were used to quantify the element's Meissner screening profiles, analyzed within a framework that accounts for nonlocal electrodynamics. The analysis indicates intrinsic length scales of λL=29.1(10)nm and ξ0=39.9(25)nm, corresponding to a Ginzburg-Landau parameter κ=0.70(5). The obtained λL and κ values, accurately quantified at the nanoscale, are smaller than those commonly used in applications and modeling, and indicate that clean niobium lies at the boundary between type-I and type-II superconductivity, supporting the contemporary view that its intrinsic state may be type I.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| Nb Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 9.25 | Pressure not reported | unknown |
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