Three-dimensional electronic structure and interband nesting in the stoichiometric superconductor LiFeAs

We report the three-dimensional electronic structure of iron pnictide superconductor LiFeAs obtained by polarization-dependent angle-resolved photoemission spectroscopy. The obtained orbital characters of each Fermi surface (FS) as well as the band dispersions were qualitatively consistent with those derived from local density approximation band calculations. It was found that FS nesting appears between a two-dimensional hole band at the zone center and an electron band at the zone corner with the same d _xy orbital character. A shadow band attributed to (π,π,π) band folding was also observed without the spin-density-wave transition. This result suggests that FS nesting between bands with the same orbital d _xy character due to spin fluctuation plays an important role in LiFeAs.