Nematic fluctuations mediated superconductivity revealed by anisotropic strain in Ba(Fe$_{1-x}$Co$_x$As)$_2$

In this presentation I will introduce anisotropic strain as an external field capable of selectively addressing the role of nematic fluctuations in promoting superconductivity in iron-based superconductors. I will present polarization-resolved elasto-Raman scattering measurements that aims at probing the evolution of nematic fluctuations under tunable strain in the normal and superconducting states of the paradigmatic iron-based superconductor Co-doped BaFe2As2. In the non-superconducting parent compound BaFe2As2the strain-induced suppression of the nematic susceptibility follows the expected behavior of an Ising order parameter under a symmetry breaking field. For the superconducting compound, the suppression of the nematic susceptibility correlates with the decrease of the superconducting critical temperature Tc. The results indicate a significant contribution of nematic fluctuations to electron pairing and validate theoretical scenarios of enhanced Tc near a nematic quantum critical point.