Spin dynamics near a putative antiferromagnetic quantum critical point in Cu-substituted BaFe2As2 and its relation to high-temperature superconductivity
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.This article is published as Kim, M. G., G. S. Tucker, S. Ran, P. C. Canfield, A. Kreyssig, A. I. Goldman, R. J. McQueeney et al. "Spin dynamics near a putative antiferromagnetic quantum critical point in Cu-substituted BaFe 2 As 2 and its relation to high-temperature superconductivity." Physical Review B 92, no. 21 (2015): 214404. DOI: 10.1103/PhysRevB.92.214404. Posted with permission.</p
