Feature-Rich Electronic Properties of Sliding Bilayer Germanene

This study employs first-principles calculations to elucidate the properties of sliding bilayer germanene (BLGe). The buckled structure of germanene can afford a greater number of metastable stacking configurations than planar graphene and enrich the electronic properties. Herein, a detailed analysis of the structural variety, shift-dependent energy bands, and spatial charge densities of BLGe is presented. The projected density of states (PDOS) reveals diverse structures such as plateaus, dips, symmetric/asymmetric peaks, and shoulders. The low-lying ones of the prominent structures could correspond to single or multiorbital hybridization, depending on the stacking configuration.

Stacking-configuration-enriched essential properties of bilayer graphenes and silicenes

First-principles calculations show that the geometric and electronic properties of silicene-related systems have diversified phenomena. Critical factors of group-IV monoelements, like buckled/planar structures, stacking configurations, layer numbers, and van der Waals interactions of bilayer composites, are considered simultaneously. The theoretical framework developed provides a concise physical and chemical picture. Delicate evaluations and analyses have been made on the optimal lattices, energy bands, and orbital-projected van Hove singularities. They provide decisive mechanisms, such as buckled/planar honeycomb lattices, multi-/single-orbital hybridizations, and significant/negligible spin-orbital couplings. We investigate the stacking-configuration-induced dramatic transformations of essential properties by relative shift in bilayer graphenes and silicenes. The lattice constant, interlayer distance, buckling height, and total energy essentially depend on the magnitude and direction of the relative shift: AA → AB → AA' → AA. Apparently, sliding bilayer systems are quite different between silicene and graphene in terms of geometric structures, electronic properties, orbital hybridizations, interlayer hopping integrals, and spin interactions.