Hidden robust presence of a hole Fermi surface in a heavily electron-doped iron-based superconductor LaFe_{2}As_{2}

Abstract

We investigate the electronic structure of a recently discovered, heavily electron-doped iron-based superconductor LaFe_{2}As_{2}. Although first-principles calculation shows apparent absence of hole Fermi surfaces around the Γ point, we reveal, by hypothetically removing the La d orbital contribution, that a hole Fermi surface around the Γ point is essentially present. In the collapsed phase of LaFe_{2}As_{2}, which is nonsuperconducting, the hole Fermi surface is found to be absent, and the difference from the uncollapsed superconducting phase can be naturally understood within the spin-fluctuation-mediated pairing scenario.