Abstract
The physical properties of two-dimensional interacting electron systems are of great current interest. An open question in the physics of low-dimensional fermionic models is whether their properties are described by standard Fermi liquid theory or whether instead they show unconventional behaviour in strongly correlated electron systems. As the two-dimensional Hubbard model is the typical example of a strongly correlated electron system, we solve for this model and its extended t–t′–U model, the two-body problem of two electrons in the vicinity of a half-filled Fermi sea. The obtained results show that for small hole concentration none of these models follow the well-known Fermi liquid picture.