Orbital Hall effect as an alternative to valley Hall effect in gapped graphene

The authors show that the valley Hall effect in gapped graphene can be understood as a manifestation of the orbital Hall effect, in which electrons in states of opposite orbital magnetic moment flow in opposite directions, generating an orbital magnetization current. Replacing the ambiguous valley indices by a physical quantity -- the orbital magnetic moment -- this reformulation provides a convincing explanation of optical rotation measurements in gapped graphene.