Quasinested Fe orbitals versus Mott-insulating V orbitals in superconducting Sr2VFeAsO3 as seen from angle-resolved photoemission

We have performed an angle-resolved photoemission spectroscopy study of the iron-based superconductor (SC) Sr2VFeAsO3. While V 3d orbitals are found to be in a Mott-insulating state and show an incoherent peak at similar to 1 eV below the Fermi level, the dispersive Fe 3d bands form several hole-and electronlike Fermi surfaces (FSs), some of which are quasinested by the (pi, 0) wave vector. This differs from the local-density approximation (LDA) calculations, which predict non-nested FSs for this material. However, LDA + U with a large effective Hubbard energy U on V 3d electrons can reproduce the experimental observation reasonably well. The observed fermiology in SC Sr2VFeAsO3 strongly supports that (pi, 0) interband scattering between quasinested FSs may play an important role for SC in pnictides.