Electronic Structure Calculations of a Jahn-Teller Active Transition Metal Oxide with Trirutile Structure*

When facing a new material exhibiting exotic phenomena like a metal-insulator transition (MIT), superconductivity, or multiferrocity, one must understand the interplay of several degrees of freedom. Our approach in this work is to use novel band structure methods based on the density functional theory (DFT) and the dynamical mean field theory (DMFT) to describe the electronic structure of a Jahn-Teller active transition metal oxide CrTa2O6 containing Cr in an unusual oxidation state of 2+, which is on the verge of a MIT. We compute the density of states, band structure, Wannier-functions, and spin density of two experimentally known structures synthesized under different conditions. The MIT is realized in one of the structures by the introduction of particular distortions, leading to a change in the orbital occupation of Cr2+. Both structures show different orbital ordering patterns but remain robust under the influence of the spin-orbit coupling and the on-site electron-electron repulsion. These results provide insight into the mechanisms leading to a MIT in oxides by tailoring the different degrees of freedom and paves the way for future electronic structure studies on similar systems.