Spin‐Polarized Transport in β‐NP and β‐NBi Nanoribbons: A First‐Principles Study

While two‐dimensional group‐V binary nanoribbons hold promise for spintronics, the synergistic effects of edge configuration and elemental substitution on their spin‐polarized transport remain unclear. Here, we combine density functional theory (DFT) and the nonequilibrium Green’s function (NEGF) method to investigate β‐NP and β‐NBi nanoribbons. Heyd–Scuseria–Ernzerhof (HSE06) hybrid functional calculations correct the spurious spin‐polarized generalized gradient approximation (SGGA) half‐metallicity, confirming that all systems are intrinsically semiconducting. We demonstrate that zigzag edges induce strong localized spin‐polarized states via symmetry breaking, whereas armchair edges exhibit weak spin splitting. Crucially, transport simulations reveal that orbital symmetry matching and transmission spectra govern the macroscopic spin‐filtering efficiency (SFE). Armchair NP achieves near‐perfect SFE (>95%) but yields sub‐microampere currents due to a severe transmission blockade, while zigzag NP suffers from unstable dual‐spin competition. In the heavier NBi series, armchair NBi is practically insulating. However, zigzag NBi perfectly balances stability and efficiency: it opens a clean transmission gap to strictly suppress the spin‐up channel, delivering stable single‐spin transport with high SFE (>94%) over most of the bias range and an appreciable current (~0.23 μA). Ultimately, while edge symmetry initiates spin polarization, heavy‐element substitution dictates its conversion into robust filtering currents, providing clear design guidelines for intrinsic 2D spintronic devices.