Quasiparticle electronic structure of Bi$_2$Se$_3$ via the sc-COHSEX+GW approach

We present ab initio calculations of the quasiparticle electronic band structure of three-dimensional topological insulator material Bi$_2$Se$_3$ using the full spinor GW approach. The mean-field is initially computed at the DFT level in the local density approximation (LDA) using fully-relativistic pseudopotentials. We then improve the mean-field electronic structure by solving Dyson's equation in the static COHSEX approximation, self-consistently updating the eigenvalues, eigenvectors, and dielectric screening. After a few iterations, we then perform a GW calculation to determine the quasiparticle energies. We compare our calculated results to experimental values of the band gaps and effective masses.