Dirac Half-Semimetallicity and Antiferromagnetism in Graphene Nanoribbon/Hexagonal Boron Nitride Heterojunctions

Half-metals have been envisioned as active componentsin spintronicdevices by virtue of their completely spin-polarized electrical currents.Actual materials hosting half-metallic phases, however, remain scarce.Here, we predict that recently fabricated heterojunctions of zigzagnanoribbons embedded in two-dimensional hexagonal boron nitride arehalf-semimetallic, featuring fully spin-polarized Dirac points atthe Fermi level. The half-semimetallicity originates from the transferof charges from hexagonal boron nitride to the embedded graphene nanoribbon.These charges give rise to opposite energy shifts of the states residingat the two edges, while preserving their intrinsic antiferromagneticexchange coupling. Upon doping, an antiferromagnetic-to-ferrimagneticphase transition occurs in these heterojunctions, with the sign ofthe excess charge controlling the spatial localization of the netmagnetic moments. Our findings demonstrate that such heterojunctionsrealize tunable one-dimensional conducting channels of spin-polarizedDirac fermions seamlessly integrated into a two-dimensional insulator,thus holding promise for the development of carbon-based spintronics.