Spin fluctuations of BaFe2(As,P)2 studied by neutron scattering

Superconductivity can be induced in parent compounds of iron-based superconductors by several methods: carrier doping, external pressure and chemical pressure. To understand their superconducting mechanism, clarifying what is a common property for achieving high-Tc superconductivity is crucial. To date, studies on spin fluctuations have been mainly performed on carrier doped samples. On the other hand, there are only a few studies on chemical pressurized samples examined by powder samples. In this work, thus, we studied spin fluctuations of P doped BaFe$_2$(As,P)$_2$ ($T_c$ = 29.5K) using single crystal samples. Inelastic neutron scattering measurements were conducted using triple axis spectrometer IN8 of ILL. As results, well-defined commensurate peaks have been observed at (0.5,0.5,$L$), which is consistent with the nesting vector of the Fermi surface. Energy spectrums at $T$ = $T_c$ show $L$ dependence, suggesting a three dimensional character remains even in superconducting BaFe$_2$(As,P)$_2$. Clear spin gap has been observed below $T_c$, whose gap structure depends on $L$. Details will be discussed at the conference.