Band Structure of Organic-Ion-Intercalated (EMIM)(x)FeSe Superconductor

The band structure and the Fermi surface of the recently discovered superconductor (EMIM) [Formula: see text] FeSe are studied within the density functional theory in the generalized gradient approximation. We show that the bands near the Fermi level are formed primarily by Fe-d orbitals. Although there is no direct contribution of EMIM orbitals to the near-Fermi level states, the presence of organic cations leads to a shift of the chemical potential. It results in the appearance of small electron pockets in the quasi-two-dimensional Fermi surface of (EMIM) [Formula: see text] FeSe.