  Lateral heterostructures of two-dimensional materials may exhibit various
intriguing emergent properties. Yet when specified to the orientationally
aligned heterojunctions of zigzag graphene and hexagonal boron nitride (hBN)
nanoribbons, realizations of the high expectations on their properties
encounter two standing hurtles. First, the rapid accumulation of strain energy
prevents large- scale fabrication. Secondly, the pronounced half-metallicity
predicted for freestanding graphene nanoribbons is severely suppressed. By
properly tailoring orientational misalignment between zigzag graphene and
chiral hBN nanoribbons, here we present a facile approach to overcome both
obstacles. Our first-principles calculations show that the strain energy
accumulation in such heterojunctions is significantly diminished for a range of
misalignments. More strikingly, the half-metallicity is substantially enhanced
from the orientationally aligned case, back to be comparable in magnitude with
the freestanding case. The restored half-metallicity is largely attributed to
the recovered superexchange interaction between the opposite heterojunction
interfaces. The present findings may have important implications in eventual
realization of graphene-based spintronics.

Mesoscale and Nanoscale Physics;Materials Science