Square selenene and tellurene: new members of elemental 2D materials with nontrivial topological properties

Elemental 2D materials are the simplest form of 2D materials, which consist of only one type of chemical elements. Yet these simple materials have various interesting properties that could lead to promising applications in a board range of fields. Many of the elemental 2D materials composed by elements from groups III to V have been predicted and even synthesized. However, few studies have been reported on the elemental 2D materials from group VI. In this talk, we will introduce two new members of elemental 2D materials composed by group VI elements Se and Te that we call square selenene and square tellurene, respectively. With first principles calculations, we predict that they have chair-like buckled structures in a square unit. This special structure gives rise to anisotropic band dispersions near the Fermi level that can be described by a generalized semi-Dirac Hamiltonian. We show that the considerably large band gap (~0.1 eV) opened by spin-orbit coupling in these materials makes them topological insulators, hosting non-trivial edge states. Finally, we show that this new type of elemental 2D materials can potentially be grown on proper substrates, such as a Au(100) surface. Our study extends the knowledge of elemental 2D materials to the group VI elements.