Strong electron correlations appear when the kinetic energy in a system is comparable or smaller than the repulsive Coulomb interaction energies. Until a few years ago this behavior was attribute in transition metal compounds almost exclusively to materials with open 3d shells, and just a few studies on a limited amount of systems have been done outside of this play ground. Only recently, it has been realised that strong correlations can appear in materials with heavy transition metal ions, due to strong spin-orbit coupling.
We will study the interplay of spin-orbit coupling and electronic correlations on a general model level. Applying continuous time quantum Monte Carlo methods to a three band model, we see that the importance of spin-orbit coupling for electronic correlations strongly depends on other system paramaters, with the electron density the most important one. Furthermore, we show that a simplistic picture using a crystal-field analogy breaks down dramatically away from half filling.