New insights into magnetically induced superconductivity
An international team of scientists under the aegis of the Integrated Infrastructures Initiative for Neutron Scattering and Muon Spectroscopy (NMI3) has discovered a new type of interaction between a magnetic field and electrons on the inside of a superconductor. The phenomenon that had not been described previously is the subject of an article in renowned Science magazine. While conducting experiments on a mono-crystal made up of Cerium, Cobalt and Indium (CeCoIn5) at the Swiss spallation neutron source (SINQ) of the Paul Scherrer Institute (PSI) in Villingen, Switzerland, the researchers from Canada, Switzerland, the UK and the USA were surprised by the formation of an unexpected electromagnetic vortex structure. These vortices were not made up of electric ring currents only. In addition, there were magnetic dipole moments (closed circulation of electric current), which increased as the magnetic field became stronger. The mono-crystal had been cooled down to -273.10°Celsius. At temperatures as low as that, all atom movement stops and the electrons in the material used form pairs, so that the material becomes superconductive and conducts electricity without loss of energy. The electron pairs and thus the state of superconductivity, however, can be destroyed by magnetic fields, which is why superconductors are usually shielded against them. Electric ring currents, and as a result electromagnetic vortices, can form when the shield is not complete. According to Michel Kenzelmann of the Paul Scherrer Insitute (PSI), these results indicate a fundamental link between magnetism and superconductivity: 'Our observations offer novel insights into the exotic characteristics of magnetically induced superconductivity', allowing conclusions about the mechanism of electron pair formation in magnetic superconductors. The researchers think that the newly discovered vortex structure is linked directly with the strong movements of the dipole moments, which act as 'glue' for the electrons and thus lead to the superconductive condensate in CeCoIn5. NMI3 brings together 23 partners from 14 countries, including 11 research infrastructures and other interested organisations. Aimed at supporting European technological development and intended as one of the 'cornerstones of the European Research Area', the initiative receives €21 million under the Sixth Framework Programme (FP6).