Fermi Surface and Band Structure of (Ca,La)FeAs₂ Superconductor from Angle-Resolved Photoemission Spectroscopy

The (Ca,R)FeAs₂ (R=La, Pr, etc.) superconductors with a signature of superconductivity transition above 40 K possess a new kind of block layers that consist of zig-zag As chains. We report the electronic structure of the new (Ca,La)FeAs₂ superconductor investigated by both band structure calculations and high resolution angle-resolved photoemission spectroscopy measurements. Band structure calculations indicate that there are four hole-like bands around the zone center Γ(0,0) and two electron-like bands near the zone corner M(π, π) in CaFeAs₂. In our angle-resolved photoemission measurements on (Ca_0.9La_0.1)FeAs₂, we have observed three hole-like bands around the Γ point and one electron-like Fermi surface near the M(π, π) point. These results provide important information to compare and contrast with the electronic structure of other iron-based compounds in understanding the superconductivity mechanism in the iron-based superconductors.