Iron-based superconductivity

Iron-based superconductivity

Since the discovery of iron-based superconductivity in 2006, the highest superconducting transition temperature (75K) is reached when a single atomic layer of iron selenide (FeSe) is deposited on SrTiO₃ or BaTiO_3. In addition to that bulk FeSe displays some of the most puzzling properties among the iron-based superconductors. Unlike all iron pnictides it exhibits 90 degree crystal rotation symmetry breaking (nematicity) without magnetic long range order. This has triggered intense debate concerning the origin of such nematicity, namely, whether it spin or orbital driven. Our workshop choose FeSe and related systems as the point for iron-based superconductors.  In a discussion session we have a participant giving a summary of the up to date development in FeSe/STO, discuss the likely role played by the substrate, and why STO is special. In addition we also have an open discussion on several competing theories for the nematicity of bulk FeSe. This important issue is directly relevant to what is the most important fluctuating degrees of freedom at the low energies, hence to the mechanism of Cooper pairing. In FeSe there is an incipient band just below the Fermi level. The effect of such incipient bands on superconductivity was also discussed in a very general context. Despite the thorough discussion no resolution is reached.