We have performed an angle-resolved photoemission spectroscopy study of the iron-based superconductor (SC) ${\mathrm{Sr}}_2{\mathrm{VFeAsO}}_3$. While V $3d$ orbitals are found to be in a Mott-insulating state and show an incoherent peak at $~1\hspace{0.5em}\mathrm{eV}$ 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 ${\mathrm{Sr}}_2{\mathrm{VFeAsO}}_3$ strongly supports that ($\pi ,0$) interband scattering between quasinested FSs may play an important role for SC in pnictides.

• Received 14 February 2011

DOI:https://doi.org/10.1103/PhysRevB.83.140513