Spin dynamics near a putative antiferromagnetic quantum critical point in Cu substituted BaFe$_2$As$_2$ and its relation to high-temperature superconductivity

M. G. Kim; M. Wang; G. S. Tucker; P. N. Valdivia; D. L. Abernathy; Songxue Chi; A. D. Christianson; A. A. Aczel; T. Hong; T. W. Heitmann; S. Ran; P. C. Canfield; E. D. Bourret-Courchesne; A. Kreyssig; D. H. Lee; A. I. Goldman; R. J. McQueeney; R. J. Birgeneau

doi:10.1103/physrevb.92.214404

arXiv · 1510.04167

Spin dynamics near a putative antiferromagnetic quantum critical point in Cu substituted BaFe$_2$As$_2$ and its relation to high-temperature superconductivity

M. G. Kim·M. Wang·G. S. Tucker·P. N. Valdivia·D. L. Abernathy·Songxue Chi·A. D. Christianson·A. A. Aczel·T. Hong·T. W. Heitmann·S. Ran·P. C. Canfield·E. D. Bourret-Courchesne·A. Kreyssig·D. H. Lee·A. I. Goldman·R. J. McQueeney·R. J. Birgeneau

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Abstract

We present the results of elastic and inelastic neutron scattering measurements on non-superconducting Ba(Fe${_{0.957}}$Cu${_{0.043}}$)${_2}$As${_2}$, a composition close to a quantum critical point between AFM ordered and paramagnetic phases. By comparing these results with the spin fluctuations in the low Cu composition as well as the parent compound BaFe$_2$As$_2$ and superconducting Ba(Fe$_{1-x}$Ni$_x$)$_2$As$_2$ compounds, we demonstrate that paramagnon-like spin fluctuations are evident in the antiferromagnetically ordered state of Ba(Fe$_{0.957}$Cu$_{0.043}$)$_2$As$_2$, 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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M. G. Kim, M. Wang, G. S. Tucker, P. N. Valdivia, D. L. Abernathy, Songxue Chi, A. D. Christianson, A. A. Aczel, T. Hong, T. W. Heitmann, S. Ran, P. C. Canfield, E. D. Bourret-Courchesne, A. Kreyssig, D. H. Lee, A. I. Goldman, R. J. McQueeney, R. J. Birgeneau. 2015-10-14. Spin dynamics near a putative antiferromagnetic quantum critical point in Cu substituted BaFe$_2$As$_2$ and its relation to high-temperature superconductivity. https://doi.org/10.1103/physrevb.92.214404

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