Soft X-ray absorption reveals magnetic impurities in Nb superconductors
Elucidating the local atomic and electronic structure of amorphous oxidized superconducting niobium films
We characterize the atomic structure of the native oxide film formed on nbresonators by comparing fluctuation electron microscopy experiments to density functional theory calculations, finding that an amorphous layer consistent with an stoichiometry.
Comparing x-ray absorption measurements at the oxygen k edge with first-principles calculations, we find evidence of d-type magnetic impurities in our sample, known to cause impedance in proximal superconductors.
Soft x-ray absorption can fingerprint magnetic impurities in these superconducting systems.
Thomas F. Harrelson, Evan Sheridan, Ellis Kennedy, John Vinson, Alpha T. N'Diaye, M. Virginia P. Altoé, Adam Schwartzberg, Irfan Siddiqi, D. Frank Ogletree, Mary C. Scott, Sinéad M. Griffin