Spin dynamics near a putative antiferromagnetic quantum critical point in Cu substituted BaFe$_2$As$_2$ and its relation to high-temperature superconductivity
We present the results of elastic and inelastic neutron scattering measurements on non-superconducting Ba(Fe0.957Cu0.043)2As2, 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 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.
@article{arxiv.1510.04167,
title = {Spin dynamics near a putative antiferromagnetic quantum critical point in Cu substituted BaFe$_2$As$_2$ and its relation to high-temperature superconductivity},
author = {M. G. Kim and M. Wang and G. S. Tucker and P. N. Valdivia and D. L. Abernathy and Songxue Chi and A. D. Christianson and A. A. Aczel and T. Hong and T. W. Heitmann and S. Ran and P. C. Canfield and E. D. Bourret-Courchesne and A. Kreyssig and D. H. Lee and A. I. Goldman and R. J. McQueeney and R. J. Birgeneau},
journal= {arXiv preprint arXiv:1510.04167},
year = {2015}
}