Design of electron correlation effects in interfaces and nanostructures

We propose that one of the best grounds for the materials design from the viewpoint of electron correlation such as ferromagnetism, superconductivity is the atomically controlled nanostructures and heterointerfaces, as theoretically demonstrated here from three examples with first-principles calculations: (i) Band ferromagnetism in a purely organic polymer of five-membered rings, where the flat-band ferromagnetism due to the electron-electron repulsion is proposed. (ii) Metal-induced gap states (MIGS) of about one atomic monolayer thick at insulator/metal heterointerfaces, recently detected experimentally, for which an exciton-mechanism superconductivity is considered. (iii) Alkali-metal doped zeolite, a class of nanostructured host-guest systems, where ferromagnetism has been experimentally discovered, for which a picture of the “supercrystal” composed of “superatoms” is proposed and Mott-insulator properties are considered. These indicate that design of electron correlation is indeed a promising avenue for nanostructures and heterointerfaces.