Superheating in coated niobium

Abstract

Using muon spin rotation it is shown that the field of first flux penetration H_entry in Nb is enhanced by about 30% if coated with an overlayer of Nb_3Sn or MgB_2. This is consistent with an increase from the lower critical magnetic field H_c1 up to the superheating field H_sh of the Nb substrate. In the experiments presented here coatings of Nb_3Sn and MgB_2 with a thickness between 50 and 2000nm have been tested. H_entry does not depend on material or thickness. This suggests that the energy barrier at the boundary between the two materials prevents flux entry up to H_sh of the substrate. A mechanism consistent with these findings is that the proximity effect recovers the stability of the energy barrier for flux penetration, which is suppressed by defects for uncoated samples. Additionally, a low temperature baked Nb sample has been tested. Here a 6% increase of H_entry was found, also pushing H_entry beyond H_c1.

6 pages, 3 figures

References in corpus (7)

• In situ epitaxial MgB2 thin films for superconducting electronics
• Unprecedented Quality Factors at Accelerating Gradients up to 45 MV/m in Niobium Superconducting Resonators via Low Temperature Nitrogen Infusion
• Superheating field of superconductors within Ginzburg-Landau theory
• Radio-frequency electromagnetic field and vortex penetration in multilayered superconductors
• Strong Meissner screening change in superconducting radio frequency cavities due to mild baking
• Superconductors in realistic geometries: Geometric edge barrier versus pinning
• Field limit and nano-scale surface topography of superconducting radio-frequency cavity made of extreme type II superconductor

Cited by in corpus (9)

• Tuning microwave losses in superconducting resonators
• Field of first flux entry and pinning strength of superconductors for RF application measured with muon spin rotation
• Depth-resolved measurements of the Meissner screening profile in surface-treated Nb
• Evidence for current suppression in superconductor-superconductor bilayers
• Measurements of the first-flux-penetration field in surface-treated and coated Nb: Distinguishing between surface pinning and an interface energy barrier
• Depth-resolved measurement of the Meissner screening profile in a niobium thin film from spin-lattice relaxation of the implanted $\beta$-emitter ${}^8$Li
• Depth-resolved Characterization of Meissner Screening Breakdown in Surface Treated Niobium
• Search for inhomogeneous Meissner screening in Nb induced by low-temperature surface treatments
• Superconducting properties of thin film $\mathrm{N}{\mathrm{b}}_{1-\mathrm{x}}\mathrm{T}{\mathrm{i}}_{\mathrm{x}}\mathrm{N}$ studied via the NMR of implanted ${}^8$Li