Quasiparticle framework

Two approaches of theoretical developments are discussed in detail in this chapter, e.g., first-principles simulations and phenomenological models. They will be unified together under the same quasiparticle framework using the full support of each other. The first-principles is very suitable for the germanene-/germanium-based emergent materials in identifying the diverse physical/chemical/material phenomena. Their geometric, electronic, magnetic and optical properties are thoroughly explored to clearly illustrate the various orbital hybridizations and spin-dependent configurations. The concise mechanisms are very useful in further understanding the intrinsic interactions for neighboring atoms and thus developing the tight-binding model/the generalized tight-binding model in the absence/presence of field perturbations. This is worthy of near-future systematic investigations. The simultaneous developments of different methods will be finished under the thorough analyses.