Spin Dependent Electronic Structure of CrI3 Based 2D Hetersotructures

Abstract

In this thesis, first-principles calculations are employed to investigate the electronic newlinestructure of 2-D van der Waals (vdW) heterostructures, with a specific focus on the newlineeffects of spin polarization and spin-orbit coupling in CrI3-based systems. The study newlineencompasses graphene, MoS2, and defect-functionalized CrI3 as key components. newlineThe first phase of the work is motivated by potential applications in magnetic storage, newlinewherein the electronic properties of a topological insulator on CrI3, serving as a magnetic newlinesubstrate, are explored. Significant phase transitions and spin-dependent bandgap newlinereductions are observed when strained MoS2 is adsorbed on CrI3, resulting in an indirect, newlinespin-independent bandgap of approximately 0.5 eV. Meanwhile, graphene s adsorption newlineon CrI3 leads to the formation of a ferromagnetic metal with a localized magnetic newlinemoment on CrI3, and the introduction of spin-orbit coupling induces a bandgap in newlinethe Dirac cone of graphene, allowing the observation of Chern insulating states without newlinethe modification of the vdW gap.In the second phase of the work, the aim is to investigate the electronic structure for newlinepotential applications in 2-D devices. In this context, graphene behaves as a semimetal, newlineCrI3 as a ferromagnetic semiconductor, and MoS2 as the insulator. The investigations newlinerevolve around the influence of magnetic tuning in inducing or suppressing Chern insulating newlinestates in graphene and the semiconductor-to-metal phase transition in MoS2. A newlinetrilayer structure, consisting of CrI3 sandwiched between graphene and MoS2, unveils newlinethe impact of lattice strain and interlayer charge transfer, resulting in a metallic trilayer. newlineIn the ferromagnetic case, graphene s Dirac cone is positioned within CrI3 s bandgap, newlineleading to the emergence of Chern insulating states. However, in the antiferromagnetic newlinescenario, graphene loses its Chern insulating properties. The introduction of spin-orbit newlinecoupling preserves the Dirac cone split of graphene within the CrI3 bandgap, enhancing newlineits Chern insulating properties.