Electronic Properties and Charge Transfer of Topologically Protected States in Hybrid Bismuthene Layers

We have performed first-principles calculations of electronic and dielectric properties of single-layer bismuth (bismuthene) adsorbed with -COOH groups. We show that in a high coverage regime, the Bi-COOH hybrid structure is a two-dimensional topological insulator with protected edge Dirac states. The adsorption process of -COOH induces a planar configuration to the initially pristine buckled bismuthene. We claim that the stability of these planar structures mainly stems from strain induced by the adsorption of the -COOH organic group, but it is also related to ligand-ligand interactions. Furthermore, we demonstrate that many-body corrections are crucial to obtain a proper description of the electronic and dielectric properties of the investigated hybrid systems. Analysis of the charge density shows that the role of this organic group is not only to stabilize the layer but also to functionalize it, which is very important for future applications such as sensing and biomolecules immobilization, as well as in electronic spintronic and even optical devices.