Valley-dependent tunneling in a monolayer gapped graphene without strain

Transmission of massive Dirac fermions in a monolayer-gapped-graphene PF/N/PF pseudo spin valve is investigated where PF is a pseudo ferromagnet caused by gap opening in graphene and N is a normal graphene sheet without energy gap. We find that, significantly, in asymmetric junction although the system has no local strain field, the valley-dependent transmission in the angular space is observed. Such transmission acting like that of electron tunneling under strain field is not observed in case of gapless graphene, saying that it is related to the influence of energy gap-like relativistic mass in graphene. We also find that, similar to fermionic field in topological insulators, energy gap between valence and conduction bands in graphene could be considered as both mass and vector potential. Our work reveals a new way to control valley currents in monolayer graphene using a gap opening, instead of using strain. It is also important for fundamental study of physics of graphene and applications of valleytronic devices.