Orbital-selective Mott transition in Sr$_2$Mn$_3$As$_2$O$_2$

Sr$_2$Mn$_3$As$_2$O$_2$ is a layered material composed of alternating cuprate-like MnO$_2$ layers and MnAs layers similar to iron pnictides [1]. Recent neutron-scattering measurements have revealed a quasi-2D Neel-AF order in the MnO$_2$ layer, along with a G-type AFM order in the MnAs layer. To better understand the experimental findings, we have performed first-principles DFT$+U$ calculations to explore the electronic structure in this material. We find the MnAs layer to be a simple Slater insulator due to the AF ordering. The MnO layer displays more correlated electron behavior that affects the transport properties. We observe a Mott transition in the MnO layer arising from the $d_{x^2-y^2}$ orbitals, reminiscent of cuprate superconductors. To study the layer- and orbital-selective Mott transition, we map the Bloch wave-functions onto Wannier orbitals with $d_{x^2-y^2}$ character. The resulting tight-binding model forms a basis for the Hubbard Hamiltonian, which we investigate using the Variational Cluster Approximation.\\ {[1]} C.-W. Chen {\it et al.}, "Orbital selective Mott transition in layered Sr$_2$Mn$_3$As$_2$O$_2$ single crystals" (under review)