The discovery of high-temperature superconductivity in iron pnic- tides raised the possibility of an unconventional superconducting mechanism in multiband materials. The observation of Fermi- surface (FS)-dependent nodeless superconducting gaps suggested that inter-FS interactions may play a crucial role in superconducting pairing. In the optimally hole-doped Ba 0.6K 0.4Fe 2As 2, the pairing strength is enhanced simultaneously (2Δ/T c≈7) on the nearly nested FS pockets, i.e., the inner hole-like (a) FS and the 2 hybridized electron-like FSs, whereas the pairing remains weak (2Δ/T c≈3.6) in the poorly nested outer hole-like (β) FS. Here, we report that in the electron-doped BaFe 1.85Co 0.15As 2, the FS nesting condition switches from the α to the β FS due to the opposite size changes for hole- and electron-like FSs upon electron doping. The strong pairing strength (2Δ/T c≈6) is also found to switch to the nested β FS, indicating an intimate connection between FS nesting and superconducting pairing, and strongly supporting the inter-FS pairing mechanism in the iron-based superconductors.
|ジャーナル||Proceedings of the National Academy of Sciences of the United States of America|
|出版ステータス||Published - 2009 5 5|
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