Comparison of rigorous vs approximate methods for accurate calculation of 2D-materials band structures and applications to THz nanoelectronics

We report on ab initio and semi-empirical techniques to investigate the electromagnetic response of 2D materials with honeycomb lattice. Band structure simulations, using density functional theory, are performed on pristine graphene and silicene. The predictions on the unique electronic features of these systems are compared to those obtained with some commonly used approaches, based on the tight-binding approximation and k.p perturbation theory. The analysis is extended to computing the surface conductivity of graphene. Our results confirm the good agreement between fundamental and approximated methods up to THz frequencies. At the same time, they show how the ab initio methods have the capability of predicting electronic properties and plasmon propagation in more realistic nano-devices, where the semi-empirical methods require further scrutiny. The above formulation will be inserted in electromagnetic full-wave solvers, for the investigation and design of 2D THz nanodevices.