Exploring Local Density of States in FeSe-based Superconductors

Starting from two Fe ions per unit cell and two degenerate orbitals per Fe ion, we construct an effective four-band model for the FeSe-based superconductors, which Fermi surfaces are consistent with those from the ARPES experiments and LDA calculations. The hole pockets at $(0,0)$ and the electron pockets at $(\pi,\pi)$ are controlled by hopping between the same orbitals on the nearest and second neighboring sites while the intervals between the inner and outer Fermi surfaces around $(0,0)$ and $(\pi,\pi)$ are determined by hopping between different orbitals on the same sublattice. On the basis of the mean field theory for superconductivity, we also investigate the local density of states for different pairing symmetries and compare them with the recent STM experiments.