Abstract
Semiconducting transition metal dichalcogenides present a complex electronic band structure with a rich orbital contribution to their valence and conduction bands. The possibility to consider the electronic states from a tight-binding model is highly useful for the calculation of many physical properties, for which first principle calculations are more demanding in computational terms when having a large number of atoms. Here, we present a set of Slater–Koster parameters for a tight-binding model that accurately reproduce the structure and the orbital character of the valence and conduction bands of single layer MX 2 , where M = Mo, W and X = S, Se. The fit of the analytical tight-binding Hamiltonian is done based on band structure from ab initio calculations. The model is used to calculate the optical conductivity of the different compounds from the Kubo formula.
Highlights
Soon after the discovery of graphene by mechanical exfoliation, this technique was applied to the isolation of other families of van der Waals materials [1]
Among them, semiconducting transition metal dichalcogenides (TMD) are of special interest because they have a gap in the optical range of the energy spectrum, which is what makes them candidates for applications in photonics and optoelectronics [2,3,4]
Another important feature of TMDs is that they present a strong spin–orbit coupling (SOC), which leads to a large splitting of the valence band at the K and K’ points of the BZ
Summary
Soon after the discovery of graphene by mechanical exfoliation, this technique was applied to the isolation of other families of van der Waals materials [1]. A direct-to-indirect gap and even a semiconducting-to-metal transition can be induced under specific conditions [5,6,7,8,9,10] They present a strong spin–orbit coupling (SOC) that, due to the absence of inversion symmetry in single layer samples, lifts the spin degeneracy of the energy bands [11]. Complicates the construction of a tight-binding (TB) model for these systems Such a TB model must be precise enough as to include all the pertinent orbitals of the relevant bands, but at the same time, simple enough as to be used without too much effort in calculations of optical and transport properties of these materials. We apply the obtained tight-binding models to calculate the optical conductivity of the four compounds
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