Interplay between Nematicity, Antiferromagnetism and Superconductivity in Iron-Based Superconductors

The antiferromagnetism, superconductivity and nematicity are three kinds of orders that have been widely seen in iron-based superconductors. Their relationship is crucial to understand the unconventional superconductivity in these materials. The antiferromagnetic ordered moment varies significantly among different materials but no experimental regular pattern is found. Moreover, whether superconductivity can be enhanced by strong nematic fluctuations is still an open question. In this talk, I will focus on the nematic fluctuations and their interaction with the antiferromagnetic order and superconductivity in iron-based superconductors. I will show that nematic fluctuations can be well studied by measuring resistivity under uniaxial pressure. The variety of the antiferromagnetic ordered moment among various parent compounds and their doped samples may be simply viewed as coming from the different amplitude of nematic fluctuations. Superconductivity will appear when nematic fluctuations are strong enough. However, superconductivity can be suppressed by enhancing nematic fluctuations under uniaxial pressure, which indicates a competition between them. Our results suggest the important role played by nematic fluctuations in iron-based superconductivity.