Localization of holes near charged defects in orbitally degenerate, doped Mott insulators

We study the role of charged defects, disorder and electron-electron (e-e) interactions in a multiband model for t(2g) electrons in vanadium perovskites R1-xCaxVO3 (R = La,...,Y). By means of unrestricted Hartree-Fock calculations, we find that the atomic multiplet structure persists up to 50% Ca doping. Using the inverse participation number, we explore the degree of localization and its doping dependence for all electronic states. The observation of strongly localized wave functions is consistent with our conjecture that doped holes form spin-orbital polarons that are strongly bound to the charged Ca2+ defects. Interestingly, the long-range e-e interactions lead to a discontinuity in the wave function size across the chemical potential, where the electron removal states are more localized than the addition states.