Electronic and optical properties of group IV two-dimensional materials

The microscopic study of complex systems has reached a high level of accuracy that allows for a deep understanding of their structure, electronic properties, and optical spectra. The theoretical investigation of surfaces is nowadays routinely done within density functional theory, for ground state properties, and, with a larger computational load, within many-body perturbation theory, for excited states properties. In this paper we present and discuss examples of calculations for group IV two-dimensional systems such as a clean silicon surface, a tin-germanium interface, graphene, and graphane, pointing out the importance of a pertinent treatment of many-body effects.