The Effect Of Spin-Orbit Coupling On Electronic Structure Of MoS₂/WSe₂ Superlattice And Pt/Co Multilayers

In this thesis, we have studied the effects of spin-orbit coupling(SOC) on electronic structure of Mo S2/WSe2 which is a potential infrared opto-electronic materials, as well as properties of [Pt/Co]n thin films which should be important in the magnetic random access memory(MRAM). All our calculations are based on density functional theory.Firstly, we investigate Mo S2/WSe2 superlattices which have continuously tunable electronic structure with direct bandgaps. The tunability is controlled by the thickness ratio of Mo S2 versus WSe2. When this ratio goes from 1:2 to 5:1, the dominant K-K direct bandgap is continuously tuned from 0.14 e V to 0.5 e V. The gap stays direct against-0.6% to 2% in-layer strain and up to-4.3% normal-layer compressive strain. Splitting of valance and conduction bands due to SOC make K and K?distinguishable. All the properties indicate that this superlattice multilayer should be a promising material for infrared optoelectronics and valley-electronics.Secondly, we find that Pt and Co atoms in(111) Pt/Co multilayer with same crystal orientation is more stable than that with opposite one. The distance between two adjacent layers(L) and magnetic moment(M) per atoms in [Pt/Co]2 is similar to those with larger n. The interfacial effects between [Pt/Co]2 multilayer and metallic oxides(Mg O and Co O) will change L, M and SOC strengths of the nearby atoms. Moreover, different contact styles have different trends of changes. This study is helpful to modulation of anomalous Hall conductivity, as well as the fundamental mechanism of anomalous Hall effect.