Hund excitations in orbital-selective Mott insulators

Multiorbital systems display a variety of novel phenomena originating in the competition between electronic, orbital, and spin degrees of freedom. Prominent among these novel effects is the orbital-selective Mott phase (OSMP), where interactions acting on a multiorbital Fermi surface cause the selective localization of electrons on one of the orbitals. It is believed that such a scenario is realized in the family of low-dimensional iron-based superconductors AFe₂X₃. In this talk, I will discuss the single-particle spectral function of the OSMP (relevant for ARPES experiments). Especially, I will focus on (i) the effect of the magnetic order present in the system and (ii) the novel band of excitations with the energy inside the Mott gap (of the corresponding single-band Hubbard model). The latter band emerges due to the Hund-exchange splitting of one of the Hubbard bands. Finally, I will discuss the frequency dependence of the optical conductivity.