Thursday, June 2, 2011

High Geekery - Iron Superconductivity

Physics - Iron superconductivity weathers another storm: "So far, the story unraveling about the new iron-based superconductors has been quite rewarding for practitioners. In order to appreciate the relevant timescales, remember that for the cuprates, nearly ten years passed before a general consensus was reached on the pairing symmetry, and consider that there still is no agreement on the underlying mechanism. More in line with the story of superconductivity in MgB2, where full consensus was achieved within a year, a plausible model was proposed within weeks after the discovery of iron-based superconductors [2] and gained support from the majority of researchers in the field. In this model, the calculated and experimentally confirmed [1] electronic band structure of iron-based superconductors is semimetallic, consisting of hole and electron Fermi surface pockets, separated by a (π,π) wave vector in momentum space (see Fig. 1). This suggests the existence of a spin excitation with the same wave vector, which was indeed found experimentally [3]. If one considers this spin excitation to be the pairing agent for superconductivity [1], the resulting order parameters for the holes and for the electrons will have opposite signs, with the overall angular momentum being L=0 (s-type); hence the name s±."

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