Band Structure and Fermi Surface of an Extremely Overdoped Iron-Based Superconductor KFe2As2

We have performed high-resolution angle-resolved photoemission spectroscopy on heavily overdoped KFe2As2 (transition temperature T-c = 3 K). We observed several renormalized bands near the Fermi level with a renormalization factor of 2-4. While the Fermi surface around the Brillouin-zone center is qualitatively similar to that of optimally doped Ba1-xKxFe2As2 (x = 0.4; T-c = 37 K), the Fermi surface topology around the zone corner (M point) is markedly different: the two electron Fermi surface pockets are completely absent due to an excess of hole doping. This result indicates that the electronic states around the M point play an important role in the high-T-c superconductivity of Ba1-xKxFe2As2 and suggests that the interband scattering via the antiferromagnetic wave vector essentially controls the Tc value in the overdoped region.