Strongly correlated metal interfaces in the Gutzwiller approximation

We study the effect of spatial inhomogeneity on the physics of a strongly correlated electron system exhibiting a metallic phase and a Mott insulating phase, represented by the simple Hubbard model. In three dimensions, we consider various geometries, including vacuum-metal-vacuum, a junction between a weakly and a strongly correlated metal, and finally the double junctions metal-Mott insulator-metal and metal-strongly correlated metal-metal. We apply the self-consistent Gutzwiller technique recently developed in our group, whose approximate nature is compensated by an extreme flexibility, ability to treat very large systems, and physical transparency. The main general result is a clear characterization of the position-dependent metallic quasiparticle spectral weight. Its behavior at interfaces reveals the ubiquitous presence of exponential decays and crossovers with decay lengths of clear physical significance. The decay length of the metallic strength in a weakly-strongly correlated metal interface is due to poor screening in the strongly correlated side. That from a metal into a Mott insulator is due to tunneling. In both cases, the decay length is a bulk property and diverges with a critical exponent (∼1/2 in the present approximation, mean field in character) as the (continuous,paramagnetic) Mott transition is approached.