• Li, L. J.
• Ding, H.
• Cao, G. H.
• Richard, P.
• Terashima, K.
• Sekiba, Y.
• Bowen, J. H.
• Kawahara, T.
• Xu, Y.-M.
• Sato, T.
• Nakayama, K.
• Xu, Z.-A.
• Takahashi, T.

Abstract

<jats:p>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<jats:sub>0.6</jats:sub>K<jats:sub>0.4</jats:sub>Fe<jats:sub>2</jats:sub>As<jats:sub>2</jats:sub>, the pairing strength is enhanced simultaneously (2Δ/T<jats:sub>c</jats:sub>≈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/T<jats:sub>c</jats:sub>≈3.6) in the poorly nested outer hole-like (β) FS. Here, we report that in the electron-doped BaFe<jats:sub>1.85</jats:sub>Co<jats:sub>0.15</jats:sub>As<jats:sub>2</jats:sub>, 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<jats:sub>c</jats:sub>≈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.</jats:p>

Topics

• impedance spectroscopy
• surface
• strength
• iron
• superconductivity
• superconductivity