Distortions to the penetration depth and coherence length of superconductor/normal-metal superlattices

P. Quarterman, Nathan Satchell, B. J. Kirby, Reza Loloee, Gavin Burnell, Norman O. Birge, J. A. Borchers
2020 PHYSICAL REVIEW MATERIALS  
Article: Quarterman, P, Satchell, N orcid.org/0000-0003-1597-2489, Kirby, BJ et al. (4 more authors) (2020) Distortions to the penetration depth and coherence length of superconductor/normal-metal superlattices. Physical Review Materials, 4 (7). 074801. Superconducting (S ) thin film superlattices composed of Nb and a normal metal spacer (N ) have been extensively utilized in Josephson junctions given their favorable surface roughness compared to Nb films of comparable thickness. In this work,
more » ... e characterize the London penetration depth and Ginzburg-Landau coherence lengths of S /N superlattices using polarized neutron reflectometry and electrical transport. Despite the normal metal spacer layers being only approximately 8% of the total superlattice thickness, we surprisingly find that the introduction of these thin N spacers between S layers leads to a dramatic increase in the measured London penetration depth compared to that of a single Nb film of comparable thickness. Using the measured values for the effective inand out-of-plane coherence lengths, we quantify the induced anisotropy of the superlattice samples and compare to a single Nb film sample. From these results, we find that that the superlattices behave similarly to layered 2D superconductors.
doi:10.1103/physrevmaterials.4.074801 fatcat:ivbbefcsfbgtdglbiujcfd6qza