Switching of intra-orbital spin excitations in electron-doped iron pnictide superconductors

Iimura, Soshi*; Matsuishi, Satoru*; Miyakawa, Masashi*; Taniguchi, Takashi*; Suzuki, Katsuhiro*; Usui, Hidetomo*; Kuroki, Kazuhiko*; Kajimoto, Ryoichi  ; Nakamura, Mitsutaka   ; Inamura, Yasuhiro  ; Ikeuchi, Kazuhiko*; Ji, S.*; Hosono, Hideo*

We investigate the doping dependence of the magnetic excitations in two-superconducting-dome-system LaFeAsOD. Using inelastic neutron scattering, spin fluctuations at different wavenumbers were observed under both superconducting domes around and 0.4, but vanished at corresponding to the valley. Theoretical calculations indicate that the characteristic doping dependence of spin fluctuations is rationally explained as a consequence of the switching of the two intra-orbital nestings within Fe-3 and 3 by electron doping. The present results imply that the multi-orbital nature plays an important role in the doping and/or material dependence of the of the iron pnictide superconductors.