Chemical bonding and surface interactions in Bi2Se3 and Bi4Se3

Topological insulators are a new class of materials that are insulators in the bulk but have near zero electron transport dissipation behavior on the surface. These surface states are topologically robust (resistant to impurities, defects, and geometry deformations), which makes these materials ideal candidates for a number of technological applications. Well-known three-dimensional topological insulators are bismuth selenide (Bi2Se3), which is composed of five-atom-thick layers that interact non-covalently with each other, and Bi–Se alloys resulting from combining these quintuple layers with elemental bismuth bilayers. In this article, we examine the surface sliding and binding energetics of the combinations of quintuple layers and bisumth bilayers found in Bi2Se3 and Bi4Se3. In addition, we investigate the nature of the chemical bonding in these systems and its relation to the surface energetics.