Jungiusstr. 11, Hörsaal AP
SFB 668 - Kolloquium
Prof. M. Allan (Leiden University):
Visualizing Electronic Nematicity and Cooper Pairing in Iron‐based Superconductors
I will present our studies on iron-based high-temperature superconductors, and introduce spectroscopic-imaging STM as a tool to understand quantum materials, by direct imaging of the relevant quantum mechanical waves on the atomic scale. The mechanism of high-temperature superconductivity is unresolved, both in terms of how the phases evolve with doping, and in terms of the actual Cooper pairing process. I will discuss our discovery of strong electronic nematicity in the parent state of iron-based superconductors, and the recent realization of how dopant-atom induced unidirectional impurity states and anisotropic scattering can explain the mysterious anisotropic transport characteristics in this material. Next, I will describe our exploration of the superconducting energy gaps and electron-boson interaction in the canonical Fe-based superconductor LiFeAs. The interactions generating unconventional Cooper pairing are often conjectured to be of electronic nature. We introduce Bogoliubov quasiparticle scattering interference (QPI) techniques for determination of both the interband scattering, the superconducting gaps in momentum space, and the electron-boson coupling self-energy. We identify strong effects in the interband direction only, pointing towards a spin-fluctuation mechanism for Cooper pairing.