Image courtesy of Argonne National Laboratory
Distribution of superconductivity around holes (white) in a thin sheet of superconducting film. Green indicates strong superconductivity. Farther away from the holes, the superconductivity decreases (yellow, red and finally black) where the material is so densely packed with vortices that they cannot move in high magnetic fields.
Increasingly high magnetic fields lower performance and eventually destroy superconductivity altogether in superconductors of all types. But high magnetic fields were found not to inhibit superconductivity but actually to protect it in ultrathin wires or in thin sheets perforated by an array of nano-sized holes.
Extension of this finding to high-temperature superconductors would enhance the use of superconducting wires in energy-relevant applications that involve high magnetic fields and lower a decades-long barrier to wider technological application of superconductors, including high-performance motors and generators.
Magnetic fields can penetrate into technologically useful (Type-II) superconductors by creating thin filaments called magnetic vortices. Only the area between is the vortices remains superconducting. However, minute vortex motion can create electrical resistance, which eliminates the remaining superconductivity. Consequently, a quest to immobilize vortices and retain zero resistance at high fields has been one of the mainstreams of superconductor research for decades. But until now all the known mechanisms of vortex immobilization or pinning have worked efficiently only at moderate magnetic fields and temperatures, thereby restricting technological and industrial applications of superconductors. An international collaboration including theory research at Argonne National Laboratory has now found a completely new approach to the problem of pinning. The team demonstrated that a wire so narrow it can accommodate only one row of vortices or a film perforated by an array of holes so close together that a only few vortices can fit between them turns high magnetic fields into healers of superconductivity rather than destroyers. At high fields, superconducting channels at the edges of the wires or holes squeeze vortices so tightly that they overlap and form clusters that can no longer move.
Materials Sciences Division, Argonne National Laboratory
Argonne, IL 60439
Department of Energy, Office of Science, Basic Energy Sciences program. Research by coauthors was supported by the Spanish MICINN and MEC, the Comunidad de Madrid, the Aragón regional Government, the Russian Academy of Sciences, and the Russian Foundation for Basic Research.
R. Córdoba et al., “Magnetic field-induced dissipation-free state in superconducting nanostructures.” Nature Communications 4, 1347 (2013). [DOI: 10.1038/ncomms2437]
Collaborations, International Collaboration