Collimation and splitting of valley electron diffraction in graphene

We reported the collimation and splitting effects of the diffraction of valley electrons in graphene. When the incident energy increases from the neutral point, the diffraction tends to be collimated for one valley and split for the other valley. The difference in the diffraction between valleys results in valley-dependent transport. We investigated the left-right conductance of a four-terminal graphene device. The conductance ratio between the two valleys was derived to be 1-(8/3)E, where E is the incident energy in units of the atom-atom hopping. The ratio is independent of the device dimensions and reflects the intrinsic properties of the electronic structure of graphene.