title: Inelastic neutron scattering study of a nonmagnetic collapsed tetragonal phase in nonsuperconducting CaFe2As2: evidence of the impact of spin fluctuations on superconductivity in the iron-arsenide compounds.
abstract: The relationship between antiferromagnetic spin fluctuations and superconductivity has become a central topic of research in studies of superconductivity in the iron pnictides. We present unambiguous evidence of the absence of magnetic fluctuations in the nonsuperconducting collapsed tetragonal phase of CaFe2As2 via inelastic neutron scattering time-of-flight data, which is consistent with the view that spin fluctuations are a necessary ingredient for unconventional superconductivity in the iron pnictides. We demonstrate that the collapsed tetragonal phase of CaFe2As2 is nonmagnetic, and discuss this result in light of recent reports of high-temperature superconductivity in the collapsed tetragonal phase of closely related compounds.
authors: Ames Laboratory, U.S. Department of Energy and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA.
authors: J H
authors: JH
authors: Soh
authors: Ames Laboratory, U.S. Department of Energy and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA.
authors: G S
authors: GS
authors: Tucker
authors: NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.
authors: D K
authors: DK
authors: Pratt
authors: Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors: D L
authors: DL
authors: Abernathy
authors: Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors: M B
authors: MB
authors: Stone
authors: Ames Laboratory, U.S. Department of Energy and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA.
authors: S
authors: S
authors: Ran
authors: Ames Laboratory, U.S. Department of Energy and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA.
authors: S L
authors: SL
authors: Bud'ko
authors: Ames Laboratory, U.S. Department of Energy and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA.
authors: P C
authors: PC
authors: Canfield
authors: Ames Laboratory, U.S. Department of Energy and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA.
authors: A
authors: A
authors: Kreyssig
authors: Ames Laboratory, U.S. Department of Energy and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA.
authors: R J
authors: RJ
authors: McQueeney
authors: Ames Laboratory, U.S. Department of Energy and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA.
authors: A I
authors: AI
authors: Goldman