An inelastic light (Raman) scattering study of nematicity and critical fluctuations in Ba(Fe1−xCox)2As2 (0≤x≤0.051) is presented. It is shown that the response from fluctuations appears only in B1g (x2−y2) symmetry. The scattering amplitude increases towards the structural transition at Ts but vanishes only below the magnetic ordering transition at TSDW<Ts, suggesting a magnetic origin of the fluctuations. The theoretical analysis explains the selection rules and the temperature dependence of the fluctuation response. These results make magnetism the favorite candidate for driving the series of transitions.%Below TSDW the gap of the magnetically ordered phase opens up.
@article{arxiv.1507.06116,
title = {Nematic fluctuations and the magneto-structural phase transition in ${\rm Ba(Fe_{1-x}Co_x)_2As_2}$},
author = {Florian Kretzschmar and Thomas Böhm and Una Karahasanović and Bernhard Muschler and Andreas Baum and Daniel Jost and Joerg Schmalian and Sergio Caprara and Marco Grilli and Carlo Di Castro and James G. Analytis and Jiun-Haw Chu and Ian Randal Fisher and Rudi Hackl},
journal= {arXiv preprint arXiv:1507.06116},
year = {2016}
}