Electronic and magnetic properties of MoS2 sheets and nanoribbons subjected to external perturbations

Student thesis: Doc typesDoctor of Sciences

Abstract

Comprehensive research on electronic and spintronic properties of graphene and MoS2 has been the focus of scientific attention for several years and still is. An important issue, however, is the presence of defects that can influence these. In the case of MoS2, experiments have demonstrated that edges (1D defect) can host local magnetic moments. However the computational cost of the ab-initio DFT calculations for experimentally relevant system size is a downside.

In this work, we first apply tight-binding numerical simulations to reproduce the band-structure of monolayer, bilayer, trilayer and bulk MoS2 2H and 3R and of monomolecular zigzag asymmetric MoS2 nanoribbons whose edge terminated by Mo atoms is passivated with sulfur dimers. The tight-binding Hamiltonian proposed by E. Cappelluti and al [Physical Review B 88, 075409 2013] is used for the planar structures. We have shown that sulfur vacancies in monolayer MoS$_2$ induce gap states in the electronic band structures. We have investigated theoretically the magnetic properties for several nanometers long MoS2 nanoribbons with zigzag edges using fine-tuned parameters in a tight-binding (TB)-Hubbard Hamiltonian. We could successfully reproduce the metallic state induced by the edges, compute large-scale nanoribbons and predict the spin domain-wall energy as well as study the effect of edge disorders on the magnetic properties. Besides the full TB parametrization of the nanoribbon, we also described the bands crossing the Fermi level with a one-dimensional linear chain model, allowing us to easily compare ferromagnetic and anti-ferromagnetic configurations and giving us a useful tool to study the energy cost for switching spins on various spots and scales. This model can be useful to study the stability and the properties of real size nanoribbons presenting spin defects and their applications.
Date of Award8 Feb 2024
Original languageEnglish
Awarding Institution
  • University of Namur
SponsorsUniversity of Namur
SupervisorLuc Henrard (Supervisor), Philippe Lambin (Co-Supervisor), Jean-Francois Colomer (President), Jean-Christophe Charlier (Jury), Robert Sporken (Jury) & Péter Vancsó (Jury)

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