A Comparison of Different Treatments of Spin-Orbit Coupling within the GW Approach

Spin-orbit coupling is responsible for the unique electronic properties of many fascinating materials such as topological insulators. We have developed and implemented an approach in which the effects of spin-orbit interactions to the quasiparticle band structure are incorporated within the GW approach, employing spinor wavefunctions computed at the DFT level with fully relativistic pseudopotentials. We compare these results to separate calculations where spin-orbit coupling is applied as a perturbation either before or after the GW calculation of the band structure. We apply these methods to the properties of materials with heavy ion cores to determine possible differences from the different schemes.