Suppression of anisotropy of kinetic energy in doped vanadium perovskites by charged defects and spin–orbital polarons

Abstract

We study the interplay of rotations of t2g-orbitals in vanadium perovskites such as La1−xSrxVO3 induced by spin–orbital polarons and by charged defects. We also analyze the resulting decay of orbital order as well as the suppression of anisotropy of kinetic energy on varying the doping. The strong local correlations and the superexchange interactions are modeled by an extended 3-orbital-flavor Hubbard–Hund model. Because of the charged defects, it is crucial to extend the model by long-range Coulomb defect potentials as well as by long-range electron–electron repulsion. Thereby, the resulting binding of doped holes (i.e., spin–orbital polarons) to negative defects leads to screening by effective dynamic dipoles. The resulting dipolar fields, in combination with disorder, control the defect states and form a soft Coulomb gap inside the Mott–Hubbard gap and thereby control the low-energy properties of the system.