  We have performed an angle-resolved photoemission spectroscopy study of a new
iron-based superconductor Sr4V2O6Fe2As2. While V 3d orbitals are found to be in
a Mott insulator state and show an incoherent peak at ~ 1 eV below the Fermi
level, the dispersive Fe 3d bands form several hole- and electron-like Fermi
surfaces (FSs), some of which are quasi-nested 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 superconducting Sr4V2O6Fe2As2
strongly supports that (pi, 0) interband scattering between quasi-nested FSs is
indispensable to superconductivity in pnictides.
