Lessons from modeling of tunneling spectroscopy on FeSe

Iron-based superconductors have been extensively studied both experimentally and theoretically over the last decade, with great progress in our understanding of these materials. Recent focus on FeSe has been centered on the connection between nematicity and superconductivity, and the possibility of enhancing T_c in monolayers on STO, or by pressure. In this talk, I will focus on two aspects of the theoretical study of tunneling spectroscopy on unconventional superconductors, 1) the physics of disorder generated local order, and 2) the understanding of recent scanning tunneling experiments mapping out the detailed spectroscopic features of FeSe by the Davis group at Cornell University. I will explain the recent evidence for orbital selective superconducting pairing, and the direct detection of orbital selective quasiparticles by quasi-particle interference. This highlights the correlated nature of FeSe, more specifically its Hund’s metal nature with coexisting orbital-dependent coherent and incoherent low-energy states. I then proceed to discuss the theoretical modelling of these phenomena and the implications for our understanding of the magnetic properties of FeSe. This is relevant for understanding the origin of superconductivity in FeSe in particular, and in the iron-based superconductors in general.