below (with two electrons per unit cell) and the doped region above (with more than two electrons per unit cell). The AF$^2$ and AF$^3$ phases are antiferromagnetic Mott insulators with two and three electrons per unit cell, respectively. The BI state is the band insulator. Intermediate between the BI and AF$^2$ phases are the excitonic insulator (EI) and an insulator with coexisting excitonic and Neél order (EI/AF). The FM, FM$^*$, PFM, and PFM$^*$ phases are all ferromagnetic metals (see Table \[tab:phases\] for the differences between these states), while PM indicates a paramagnetic metallic phase. All the metallic states above exhibit excitonic order.[]{data-label="partialfig"}](pdspec.eps){width="3.25in"}

To provide a concrete demonstration of these ideas, the strong coupling zero temperature phase diagram of the model is calculated in this paper using a “free Fermi gas” approximation. This approximation captures the most important [*single quasiparticle*]{} physics of electronic propagation in an excitonically-ordered background, but neglects interactions between these quasiparticles. For simplicity, we also assume a [*fixed amplitude*]{}, ${\rm Tr}\,
\Delta^\dagger \Delta^{\vphantom\dagger} = \Delta_0^2/2$, of the excitonic order parameter. The latter assumption is valid for weak doping, $x \ll 1$, in which the [*orientation*]{} of the ordering is of paramount importance. Putting together the results of this 