Hidden robust presence of a hole Fermi surface in a heavily electron-doped iron-based superconductor LaFe2As2

Abstract

We investigate the electronic structure of a recently discovered, heavily electron-doped iron-based superconductor LaFe2As2. 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 LaFe2As2, 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.