On nematicity, magnetism and superconductivity in FeSe

FeSe provides a new perspective on the intensively studied phase interplay in iron-based materials. At ambient pressure, FeSe exhibits the typical (nematic) structural phase transition, but, unusually, no long-range magnetic order and no competition between nematicity and superconductivity. Under pressure, the structural transition is gradually suppressed and a new, likely magnetic phase emerges. I will present our recent results on the nematic phase and the pressure-temperature phase diagram of vapor-grown single crystals of FeSe. The origin of the nematic resistivity anisotropy at ambient pressure and the pressure evolution of the orthorhombic distortion, the superconducting upper critical field and magnetic ordering are investigated using resistivity, elastoresistivity, diffraction and synchrotron Moessbauer spectroscopy. The relation of magnetism, structure and superconductivity in FeSe will be discussed and compared to other iron-based systems.