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Spin dynamics near a putative antiferromagnetic quantum critical point in Cu-substituted BaFe2As2 and its relation to high-temperature superconductivity

  • Author(s): Kim, MG
  • Wang, M
  • Tucker, GS
  • Valdivia, PN
  • Abernathy, DL
  • Chi, S
  • Christianson, AD
  • Aczel, AA
  • Hong, T
  • Heitmann, TW
  • Ran, S
  • Canfield, PC
  • Bourret-Courchesne, ED
  • Kreyssig, A
  • Lee, DH
  • Goldman, AI
  • McQueeney, RJ
  • Birgeneau, RJ
  • et al.

We present the results of elastic and inelastic neutron scattering measurements on nonsuperconducting Ba(Fe0.957Cu0.043)2As2, a composition close to a quantum critical point between antiferromagnetic (AFM) ordered and paramagnetic phases. By comparing these results with the spin fluctuations in the low-Cu composition as well as the parent compound BaFe2As2 and superconducting Ba(Fe1-xNix)2As2 compounds, we demonstrate that paramagnon-like spin fluctuations are evident in the antiferromagnetically ordered state of Ba(Fe0.957Cu0.043)2As2, which is distinct from the AFM-like spin fluctuations in the superconducting compounds. Our observations suggest that Cu substitution decouples the interaction between quasiparticles and the spin fluctuations. We also show that the spin-spin correlation length ξ(T) increases rapidly as the temperature is lowered and find ω/T scaling behavior, the hallmark of quantum criticality, at an antiferromagnetic quantum critical point.

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