Terashima K, Sekiba Y, Bowen J H, Nakayama K, Kawahara T, Sato T, Richard P, Xu Y-M, Li L J, Cao G H, Xu Z-A, Ding H, Takahashi T
Ultraviolet Synchrotron Orbital Radiation Facility, Institute for Molecular Science, Okazaki 444-8585, Japan.
Proc Natl Acad Sci U S A. 2009 May 5;106(18):7330-3. doi: 10.1073/pnas.0900469106. Epub 2009 Apr 9.
The discovery of high-temperature superconductivity in iron pnictides 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(0.6)K(0.4)Fe(2)As(2), the pairing strength is enhanced simultaneously (2Delta/T(c) approximately 7) on the nearly nested FS pockets, i.e., the inner hole-like (alpha) FS and the 2 hybridized electron-like FSs, whereas the pairing remains weak (2Delta/T(c) approximately 3.6) in the poorly nested outer hole-like (beta) FS. Here, we report that in the electron-doped BaFe(1.85)Co(0.15)As(2), the FS nesting condition switches from the alpha to the beta FS due to the opposite size changes for hole- and electron-like FSs upon electron doping. The strong pairing strength (2Delta/T(c) approximately 6) is also found to switch to the nested beta FS, indicating an intimate connection between FS nesting and superconducting pairing, and strongly supporting the inter-FS pairing mechanism in the iron-based superconductors.
铁基氮化物中高温超导性的发现，引发了多带材料中存在非常规超导机制的可能性。对依赖费米面（FS）的无节点超导能隙的观测表明，费米面间相互作用可能在超导配对中起关键作用。在最佳空穴掺杂的Ba(0.6)K(0.4)Fe(2)As(2)中，在近乎嵌套的费米面上，即内部类空穴（α）费米面和2个杂化类电子费米面，配对强度同时增强（2Δ/Tc约为7），而在嵌套较差的外部类空穴（β）费米面上，配对仍然较弱（2Δ/Tc约为3.6）。在此，我们报道，在电子掺杂的BaFe(1.85)Co(0.15)As(2)中，由于电子掺杂时类空穴和类电子费米面尺寸变化相反，费米面嵌套条件从α费米面转变为β费米面。还发现强配对强度（2Δ/Tc约为6）也转移到了嵌套的β费米面上，这表明费米面嵌套与超导配对之间存在紧密联系，并有力地支持了铁基超导体中的费米面间配对机制。
