Berlin 2018 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 35: Superconductivity: Fe-based Superconductors - 122 and Theory

TT 35.1: Talk

Tuesday, March 13, 2018, 09:30–09:45, A 053

Soft phonons reveal finite nematic correlation length in Ba(Fe_0.94Co_0.06)₂As₂ — •Frank Weber¹, Michael Merz¹, Thomas Wolf¹, Rafael Fernandes², Jörg Schmalian¹, and Dmitry Reznik³ — ¹Institute for Solid State Physics, Karlsruhe Institute of Technology, Karlsruhe, Germany — ²School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota, 55455, USA — ³Department of Physics, University of Colorado at Boulder, Boulder, Colorado, 80309, USA

Nematicity is ubiquitous in electronic phases of high-T_c superconductors, particularly in the Fe-based systems. While several experiments have probed nematic fluctuations, they have either been restricted to uniform, i.e. q=0 fluctuations, or measure momentum-averaged effects. Here, we investigate the behavior of finite-momentum nematic fluctuations near q≈ 0 by utilizing the anomalous softening of transverse acoustic phonon modes in optimally doped Ba(Fe_0.94Co_0.06)₂As₂. We determine the nematic correlation length and find that it sharply changes its T-dependence at T_c, revealing a strong connection between nematicity and superconductivity.