Tunable anisotropic electronic transport in bilayer phosphorene Y-junctions

We theoretically investigate the electronic transport properties of three-terminal ballistic junctions based on bilayer phosphorene nanoribbons, subjected to a uniform perpendicular electric field. We exploit the intrinsic anisotropy of phosphorene by considering different edge terminations for the nanoribbons that form such junctions, namely normal armchair, normal zigzag, skewed armchair, and skewed zigzag. Unlike bilayer graphene, the Bernal-stacked bilayer phosphorene, when subjected to an inversion symmetry breaking, such as the application of a perpendicular electric field, exhibits a semiconductor to metal transition, whereas in AB-stacked bilayer graphene, one observes a gap opening and a metal to semiconductor transition instead. Thus, by adopting this electric-field-controlled band gap strategy for bilayer phosphorene, we demonstrate the possibility of modulating the current flowing through bilayer-BP-based Y-junctions, redirecting it to one or both output terminals under specific conditions. The role played on the electron conductance and probability density currents by the different Y-junction constituents is also explored, and such results are interpreted in light of nanoribbons' dispersion relations. In this sense, the proposed system acts as a nanoscale switching device, and its current modulation effect can be used to develop phosphorene-based logic gates with a large on/off current ratio, benefiting from the material's high carrier mobility.