Regensburg 2019 – wissenschaftliches Programm
TT 15.10: Hauptvortrag
Montag, 1. April 2019, 17:30–18:00, H23
Theory of superconducting pairing in iron-based superconductors — •Andreas Kreisel — Universität Leipzig, Germany
Theoretical studies of high temperature superconductivity seem to struggle with the question whether the electronic states should be treated in an itinerant approach or using a picture where electrons are almost localized. In the case of iron-based materials, both approaches can explain a number of physical effects and the appearance of various phases. Guided by recent experimental results in the superconducting phase, we use a spin-fluctuation pairing theory that also contains low-energy aspects of strong correlations. A main ingredient of this itinerant approach is to incorporate reduced coherence of quasiparticles occupying specific orbital states into the description of the Fermi liquid. It is demonstrated that this paradigm yields remarkably good agreement with the experimentally observed anisotropic gap structure in 3 different materials: Bulk and monolayer FeSe, as well as LiFeAs. The first system has created a lot of interest recently, because it shows a strong anisotropy in its nematic state. For a deeper understanding of the connection to the Fermi liquid picture, we study the magnetic excitation spectrum  and consequences for the vortex formation in the superconducting state and discuss these in view of recent inelastic neutron scattering data and magnetic penetration depth measurements.
A. Kreisel, Brian M. Andersen, P. J. Hirschfeld, arXiv:1807.09482
P. Biswas, et al., Phys. Rev. B 98, 180501(R) (2018)