Transições tipo-Peierls em MoS2 semi-hidrogenado: estudo por primeiros princípios

Abstract

We apply a first principles formalism based on the density functional theory to study structural, electronic and magnetic properties of semi-hydrogenated monolayer molybdenum disulfide. We consider a complete functionalization of the sulphur atoms of the upper MoS2 surface, and we investigated, firstly, the emergence of structural transitions. In fact, we found that the resulting structure with the lowest energy has a deformation in the form of a double dimerization of lines of Mo atoms, leading to a description based on a 2x2 primitive cell. The dimerization, moreover, is responsible for the opening of a bandgap in the electronic structure - the system, if described in a 1x1 cell, is metallic. The phenomenology is consistent, thus, with a two-dimensional Peierls-like transition. In addition, we verified, by including the spin variables, the existence of a series of metastable structures, among them we highlight the appearance of a 1T phase that can present ferromagnetic or antiferromagnetic orderings. In particular, in the latter case, we found that a deformation, also based on dimerization of Mo lines, could decrease the energy of the system in relation to the original AF structure, in a transition which can be associated with a spin-Peierls phenomenology. Finally, the stability of the lowest energy structure was verified by means of the calculating of the phonon spectrum.