Valley Pseudospin with a Widely Tunable Bandgap in Doped Honeycomb BN Monolayer.

Valleytronics is a promising paradigm to explore the emergent degree of freedom for charge carriers on the energy band edges. Using ab initio calculations, we reveal that the honeycomb boron nitride (h-BN) monolayer shows a pair of inequivalent valleys in the vicinities of the vertices of hexagonal Brillouin zone even without the protection of the C symmetry. The inequivalent valleys give rise to a 2-fold degree of freedom named the valley pseudospin.