  We propose a practical scheme to generate a pure valley current in monolayer
transition metal dichalcogenides by one-photon absorption of linearly polarized
light. We show that the pure valley current can be detected by either
photoluminescence measurements or the ultrafast pump-probe technique. Our
method, together with the previously demonstrated generation of valley
polarization, opens up the exciting possibility of ultrafast optical-only
manipulation of the valley index. The tilted field effect on the valley current
in experiment is also discussed.
