Bilayer germanene/germanene composites

The composite condensed-matter systems, which consist of two different monolayer subsystems, are formed by the intrinsic interlayer atomic interactions, e.g., the significant van Der Waals interactions. The various coupled materials are expected to exhibit the diverse phenomena. They are very suitable for the experimental verifications about the 2D well-known theories. The bilayer Si-Ge composite systems present the diversified essential properties. The critical mechanisms, the weak, but significant van der Walls interactions in the non-unifrom enlarged unit cells, the sp3 bondings on silicene/germanene, and the important spin-orbital couplings. The first factor is revealed in the interlayer distances, being comparable to those in bilayer graphene systems. The concise physical & chemical pictures are further confirmed from the atom-dominated band structures, the total charge density distributions & their variations after coupling, and the atom- & orbital-decomposed van Hove singularities. The ferrommagnetic or anti-ferromagnetic configurations are absent in three kinds of composite systems.