Spin Gaps in Transition Metal Dichalcogenide Nanoribbons with Atomic Adsorbates

Edge-functionalized transition metal dichalcogenide nanoribbons of the zigzag type (zTMDCNRs) are explored in terms of their spin transmission properties. Specifically, systems of the type 5-zWXYNR+nad (X, Y = S, Se; n = 0 1, 2; ad = H, B, C, N, and O), involving five rows of a zWXY unit, are investigated as transmission elements between semi-infinite electrodes to identify atomic adsorbates and adsorption conditions for maximizing the spin polarization of current traversing the ribbons. Janus counterparts of these units, asymmetric structures comprising a transition metal layer sandwiched by two different chalcogen layers, are included in this study. In all cases considered, density functional theory modeling, involving the hybrid Heyd–Scuseria–Ernzerhof exchange–correlation functional, is combined with the nonequilibrium Green’s function approach to determine both spin and charge transport properties. The effect of selected atomic absorbates on the geometric, electronic, and magnetic properties of 5-zWXYNR (X, Y = S, Se) is evaluated. A protocol is formulated to assess the spin-filtering capacity of 5-zWXYNR+nad as a function of the nature and the density of atomic adsorbates, in terms of electrode band structure analysis. Spin gaps emerging close to the Fermi energy of the electrode are shown to provide an effective predictor of the degree of current spin polarization achieved by any of the transmission systems studied here. For any adsorbate configuration considered, ferromagnetic and antiferromagnetic ordering is examined and the impact of the magnetic phase on the spin-transport properties is discussed. A spin-selective negative differential resistance effect is identified in the pristine nanoribbon systems.