Electronic structure of the new Ni-based superconductor KNi2Se2.

The electronic structure of the newly discovered superconductor KNi(2)Se(2) is studied by first-principles calculations. Our results show that its ground state is a quasi-two-dimensional metal and the Fermi surface is contributed by the Ni 3d and Se 4p states. These states determine the significant physical properties of the heavy-fermion superconductor KNi(2)Se(2), such as the heavy-fermion behavior and low superconducting transition temperature. Based on the multi-orbital character of our calculation, we suggest that KNi(2)Se(2) may have a complicated superconducting multi-gap structure. The influence of the Coulomb interaction on the electronic structure and the 3d orbital character in this material is also investigated.