title: Universality of the dispersive spin-resonance mode in superconducting BaFe2As2.
abstract: Spin fluctuations in superconducting BaFe2(As(1-x)P(x))2 (x=0.34, T(c)=29.5 K) are studied using inelastic neutron scattering. Well-defined commensurate magnetic signals are observed at (π, 0), which is consistent with the nesting vector of the Fermi surface. Antiferromagnetic (AFM) spin fluctuations in the normal state exhibit a three-dimensional character reminiscent of the AFM order in nondoped BaFe2As2. A clear spin gap is observed in the superconducting phase forming a peak whose energy is significantly dispersed along the c axis. The bandwidth of dispersion becomes larger with approaching the AFM ordered phase universally in all superconducting BaFe2As2, indicating that the dispersive feature is attributed to three-dimensional AFM correlations. The results suggest a strong relationship between the magnetism and superconductivity.
authors.affiliation: National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568, Japan and Transformative Research-Project on Iron Pnictides (TRIP), JST, Chiyoda, Tokyo 102-0075, Japan.
authors.forename: C H
authors.initials: CH
authors.lastname: Lee
authors.forename: P
authors.initials: P
authors.lastname: Steffens
authors.forename: N
authors.initials: N
authors.lastname: Qureshi
authors.forename: M
authors.initials: M
authors.lastname: Nakajima
authors.forename: K
authors.initials: K
authors.lastname: Kihou
authors.forename: A
authors.initials: A
authors.lastname: Iyo
authors.forename: H
authors.initials: H
authors.lastname: Eisaki
authors.forename: M
authors.initials: M
authors.lastname: Braden