Orbital-selective electronic localization in dimerized NbO2 : From Peierls to Mott

We present a theoretical investigation of the t2g electronic structure reconstruction of body-centered-tetragonal (bct) NbO₂ employing a combination of density functional theory and dimer-embedded dynamical mean-field theory calculations. We describe the electronic structure of the insulating phase of bct NbO₂ and propose an orbital-selective mechanism for the gap opening. The resulting insulating state of the dimerized x²-y² orbital along the rutile c axis is shown to be adiabatically connected to an entangled Mott-Peierls insulator, but the true nature of insulating bct NbO₂ compared with experiment is better characterized as a Mott localized electronic state due to strong dynamical intrasite multiorbital correlations. Our orbital-selective, strong-coupling scenario could be tested in future studies of NbO₂ Mott memristors for neuromorphic computing.