FERMI SURFACE NESTING INDUCED STRONG PAIRING IN IRON-BASED SUPERCONDUCTORS

DOI: 10.1073/pnas.0900469106
Journal:  Nature
Year of Publication: 2009
Volume: 1062009
Issue: 18
Authors: K. TerashimaY. SekibaJ. H. BowenK. NakayamaT. KawaharaT. SatoP. RichardY.-M. XuL. J. LiG. H. CaoZ.-A. XuH. DingT. Takahashi

Abstruct

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 Ba0.6K0.4Fe2As2, the pairing strength is enhanced simultaneously (2Δ/Tc≈7) on the nearly nested FS pockets, i.e., the inner hole-like (α) FS and the 2 hybridized electron-like FSs, whereas the pairing remains weak (2Δ/Tc≈3.6) in the poorly nested outer hole-like (β) FS. Here, we report that in the electron-doped BaFe1.85Co0.15As2, 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/Tc≈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.

Keyword:
Angle-resolved photoemission, band structure, iron pnictide, superconductivity