Doping excitonic insulator: a way to new quantum states

Abstract: Excitonic magnetism, also called van Vleck magnetism, is a new phenomenon that has been theoretically proposed in strongly correlated materials with non-magnetic atomic ground states. I will describe the strong-coupling approach to this phenomenon and explain its connection to Bose-Einstein condensation of spinful bosons. I will present numerical result obtained for two-band Hubbard model with dynamical mean-field theory. Particularly interesting is the observation of k-space spin texture in a centrosymmetric system without spin-orbit coupling. An analytic theory reveals a mechanism similar to Zener double-exchange and suggests directions where to search for states with unusual properties.