First-Principles Study of the Electronic Structure of Heavy Fermion YbNi₂

Abstract

We investigate the electronic properties of YbNi₂ by means of band structure calculations based on the density functional theory within LDA (local density approximation), fully relativistic, and LDA+U schemes. The 4f derived bands are studied within a relativistic framework which yields flat and spin-orbit split bands, and a correlated band method (LDA+U) that includes correlation corrections. In both cases, the 4f bands, which is located roughly 200 meV below the Fermi level (E _F ), hybridize weakly with the dispersive Ni-3d bands. When the fully relativistic scheme is applied, the 4f derived bands split into lower and higher bands due to spin-orbit coupling effects. The 4f electrons are delocalized through the hybridization with conduction electrons, and the hybridization between f and conduction d electrons also plays a important role in YbNi₂. The on-site Coulomb potential is added to the Yb-derived 4f orbitals, the degeneracy between the 4f orbitals would be lifted partially and they are split into three manifolds bands. The Fermi surface splits into three different sheets which are from main the Yb-4f derived bands and Ni-3d bands. Band structure calculations reveal a saddle points existence at the L point in the energy dispersion curve closed to E _F , whereby, we think YbNi₂ might have a superconducting properties. In addition, the quasiparticle mass enhancement inferred by comparing γ to the density of states (DOS) at the Fermi level indicates the effective mass of YbNi₂ enhanced with the fully relativistic results.