Niobium in the clean limit: An intrinsic type-I superconductor

FeTe0.55Se0.45: A multiband superconductor in the clean and dirty limit

The detailed optical properties of the multiband iron-chalcogenide superconductor FeTe0.55Se0.45 have been reexamined for a large number of temperatures above and below the critical temperature Tc = 14 K for light polarized in the a-b planes. Instead of the simple Drude model that assumes a single band, above Tc the normal-state optical properties are best described by the two-Drude model that ...

Interference effects on the critical current in a clean-limit superconductor-normal-metal-superconductor junction.

Study of Ultra-clean Surface for Niobium SC Cavities

For a TeV energy particle physics, R&D of electron/positron linear colliders has been conducted very hard at many laboratories. Development of high field gradient cavities is one of key issues to realize such a machine. Field emission loading is a dominant phenomenon limiting high field. Particulate contamination on the inner surface is a main source of field emission. In this paper, we report ...

Hydrogen-dislocation Interactions and Intrinsic Dislocation Relaxation in Niobium

The dislocation relaxation between 100 K and 200 K (IkHz) in plastically deformed niobium, formerly named "a-relaxation" is a hydrogen Snoek-Koster relaxation (cold work relaxation). This is shown by experiments on extremely degassed samples, which contained controlled amounts of hydrogen and/or oxygen. The intrinsic, hydrogen-free dislocation relaxation appears between 30 K and 70 K (IkHz), th...

Critical velocity of a clean one-dimensional superconductor

We revisit the problem of critical velocity of a clean one-dimensional superconductor. At the level of mean-field theory, we find that the zero-temperature value of the critical velocity—the uniform velocity of the superfluid condensate at which the superconducting state becomes unstable—is a factor of 2 smaller than the Landau critical velocity. This is in contrast to a prior finding, which he...