Angle-resolved spectroscopy study of Ni-based superconductor SrNi2As2

We performed an angle-resolved photoemission spectroscopy study of the Ni-based superconductor SrNi2As2. Electron and hole Fermi surface pockets are observed, but their different shapes and sizes lead to very poor nesting conditions. The experimental electronic band structure of SrNi2As2 is in good agreement with first-principles calculations after a slight renormalization (by a factor 1.1), confirming the picture of Hund's exchange-dominated electronic correlations decreasing with increasing filling of the 3d shell in the Fe-, Co-, and Ni-based compounds. These findings emphasize the importance of Hund's coupling and 3d-orbital filling as key tuning parameters of electronic correlations in transition-metal pnictides.