Ab-initio quantum transport in two-dimensional materials

Two-dimensional (2D) magnets present exciting opportunities for next-generation nanoelectronics and spintronics, though a comprehensive understanding of their transport characteristics remains an active area of research. In this thesis, we employ first-principles density-functional theory combined with non-equilibrium Green's function methods (DFT+NEGF). This allows us to investigate how atomic-scale interfaces, spin–orbit coupling, magnetic ordering and switching phenomena, and electron–phonon coupling influence quantum transport in graphene and borophene nanoribbons, as well as in magnetic van der Waals (vdW) heterostructures based on Fe4GeTe2 and VSe2. First, realistic Wannier-derived tight-binding models substantially enhance predictions of transport phenomena in graphene nanoribbons, clearly illustrating the effects of perpendicular electric fields and charged impurities on conductance properties. Second, our simulations reveal exceptional spin-filtering performance in vdW heterostructures incorporating Fe4GeTe2 achieving nearly ideal spin polarization (up to 97%) and remarkably high tunnel magnetoresistance (TMR > 480% in low bias) in multilayer magnetic tunnel junctions (MTJs). Third, we explored spin-transfer torque (STT) efficiency in MTJs consisting of monolayer 1T-VSe2 ferromagnets, MoS2 tunneling barriers, and tantalum disulfide (TaS2) electrodes in different structural polytypes (1T and 2H). Our detailed computational analysis reveals that the choice of TaS2 polytype has a significant influence on spin-dependent transport, critical current density, and Gilbert damping. These findings highlight the crucial role of atomic-level structural tuning in optimizing STT-driven magnetization switching. Finally, electron–phonon coupling is found to enhance spin currents in borophene nanoribbons and monolayer VSe2 by enabling additional conduction channels through inelastic scattering processes. This underlines lattice vibrations as an essential element for the strategic engineering of spintronic devices. Collectively, these results deepen our understanding of quantum transport in 2D magnetic systems and deliver concrete strategies for advancing nanoelectronic and spintronic device design.