Manipulation Of Magnetic,Electronic And Valleytronic Properties Of Two-dimensional Materials

Recent years,integrated circuits(IC)are gradually developing towards miniaturization,high density,low power consumption,non-volatile and high speed.Due to dimensionality reduction and quantum confinement effect,two-dimensional materials exhibit excellent properties different from bulk material,and become the focus of attention in the field of information technology.At present,a variety of two-dimensional materials have been found experimentally,such as graphene,transition metal dihalides,metal oxides and two-dimensional magnets.However,modern technology and applications require materials to possess multifunctional effects to achieve functional integration,and it is difficult for a single material to achieve multiple functions without modification.The electrical,magnetic,and optical properties of two-dimensional layered materials can be flexibly regulated through different methods,such as strain,gating,ion doping and heterojunction construction,so as to achieve a variety of functional effects.In the field of physical electronics,it has become an important research direction to explore the regulation methods and effects of the properties of two-dimensional materials.In the article,by using the first principles calculation method based on density functional theory,a typical two-dimensional transition metal dihalides MX₂(X=Mo,W;X=S,Se,Te)and ferromagnetic metal Fe₃Ge Te₂ were taken as examples,in order to investigate the regulation of intrinsic electronic,valleytronic and magnetic properties of two-dimensional layered materials,with electrical methods(such as external electric field,charge injection,ferroelectric polarization reversal),which provides certain theoretical guidance for the development of spintronics and the application of new multifunctional devices.The article mainly includes two parts:1.The intrinsic electronic properties of six MX₂ monolayers of H phase is studied,and we analyze the regulation of external electric field on Rashba spin splitting.The movement of near free electron states on the band structure of MX₂ monolayer with external electric field and electron doing.In addition,we also compare the variation of nearly free electron states in the distort T phase Mo Te₂ monolayer and WTe₂ monolayer with corresponding H phase.Finally,the reason of ferromagnetism and valley polarization induced by charge doping in Mo Te₂ monolayer is explained simply.2.We investigate the intrinsic ferromagnetism and magnetic anisotropy of Fe₃Ge Te₂ monolayer,and analyze the dependence of the magnetic anisotropy of Fe₃Ge Te₂ monolayer on the spin-orbit coupling of Te atoms by replacing Te atom with Se atom of the same group.With the electrical method of hole doping and the construction of ferromagnetic/ferroelectric heterojunction(Fe₃Ge Te₂/In₂Se₃),the magnetic anisotropy energy of Fe₃Ge Te₂ is modified.