FeAs superconductors
Superconductivity without nesting in LiFeAs
We have studied the electronic structure of the non-magnetic LiFeAs (Tc~18K) superconductor using angle-resolved photoemission spectroscopy. We find a notable absence of the Fermi surface nesting, strong renormalization of the conduction bands by a factor of three, high density of states at the Fermi level caused by a Van Hove singularity, and no evidence for either a static or fluctuating order except superconductivity with in-plane isotropic energy gaps. Our observations suggest that these electronic properties capture the majority of ingredients necessary for the superconductivity in iron pnictides.
Figure Fermi surface shape and topology. a) Momentum distribution map of the photoemission intensity integrated within 5 meV around the Fermi level. Solid black lines represent Gamma - centered Fermi contours, dashed lines – most pronounced M-centered Fermi contours. b,c) Momentum-energy cuts along the vertical directions marked by the white dashed lines in panel a).