---

The discovery of superconductivity in Fe-based superconductors in 2008 with Tc reaching almost 60K is among the most significant breakthroughs in contemporary condensed matter physics. The experimental data on superconductivity show rich behavior, with potentially different symmetry of a superconducting state for different compositions of the same material. Furthermore, the phase diagram reveal a complex interplay between magnetism and superconductivity typical for other exotic superconductors such as cuprates or heavy fermions. In my talk I will present an introduction to various aspects of the theory of iron-based superconductors. In particular, I will discuss general aspects of the Cooper-pairing in Fe-based superconductors. I will argue that the physics is universal and that all pairing states obtained so far can be understood within the same universal pairing scenario. Then I will review the magnetic ordering in the iron-based parent compounds. I will first analyze the selection of the experimentally observed magnetic order out of the degenerate manifold which occurs due to frustration associated with multiple nesting wave vectors. In addition, in analogy to the J1-J2 model of the localized spins, I will discuss the possibility of an Ising nematic order to form above the actual Neel temperature and its coupling to orbital and lattice degrees of freedom.

---

Prof. Dr. Ilya Eremin, Ruhr-Universität Bochum
Seminarraum des II. Physikalischen Instituts
Contact: not specified