\\
& + U \sum_{i\alpha} n_{i\alpha\uparrow} n_{i\alpha\downarrow}
\end{aligned}$$

where $\langle i, j\rangle$ denotes nearest-neighbor lattice cells, $\alpha=\{1,2\}$ denote the dimer orbitals within a given cell, $\sigma$ is the spin, $t$ is the lattice (i.e. inter-dimer) hopping and ($t_\perp$) is the intra-dimer hopping. The parameter $U$ is the on-site Coulomb repulsion.

The non-interacting limit of the DHM has two bands which are locally hybridized at every lattice cell site. This leads to the parallel splitting of the two bands by $2t_\perp$. When this splitting is large enough, the system has a continuous metal insulator transition. We associate this to a Peierls-like mechanism, as it is driven by the increase of the intra-dimer hopping amplitude $t_\perp$. It can be ascribed to a schematic representation of the monoclinic distortion in the real material that creates dimers in the unit cell (see Fig. \[fig0\]). Another way to see this IMT is by starting from the $t \to 0$ limit, where the local dimers that form a bonding (B) and an anti-bonding (AB) molecular orbital at every 1-2 link. Switching on the inter-dimer hopping, these orbitals lead to an insulating state with two split flat bands. At a large enough (lattice-geometry dependent) value of $t$, 