Anderson localization for two interacting electrons in a disordered chain

We present an exact diagonalization study of the localization properties and the corresponding dynamics for two electrons interacting via on-site Hubbard terms in a finite disordered chain, We obtain three kinds of two-electron states: (i) states almost unchanged by the interaction with the two electrons well separated from each other, (ii) others with the localization length increased by the interaction, and (iii) states for which the interaction decreases the localization length. The physical origin of these states and their distribution in the band is examined from weak to strong interactions.