Nematicity is ubiquitous in electronic phases of high-Tc superconductors, particularly in the Fe-based systems. While several experiments have probed nematic fluctuations, they have been restricted to uniform or momentum-averaged fluctuations. Here, we investigate the behavior of finite-momentum nematic fluctuations by utilizing the anomalous softening of acoustic phonon modes in optimally doped Ba(Fe0.94Co0.06)2As2. We determine the nematic correlation length and find that it sharply changes its T dependence at Tc, revealing a strong connection between nematicity and superconductivity.
Bibliographical noteFunding Information:
F.W. was supported by the Helmholtz Young Investigator Group under Contract No. VH-NG-840. M.M. was supported by the Karlsruhe Nano-Micro Facility (KNMF). D.R. was supported by the DOE, Office of Basic Energy Sciences, Office of Science, under Contract No. DE-SC0006939. R.M.F. and M.S. are supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Award No. DE-SC0012336. Part of the work by D.R. and J.S. was performed at the Aspen Center for Physics, which is supported by National Science Foundation Grant No. PHY-1607611.