  We show that, because of the inevitable twist and lattice mismatch in
heterobilayers of transition metal dichalcogenides, interlayer excitons have
six-fold degenerate light cones anomalously located at finite velocities on the
parabolic energy dispersion. The photon emissions at each light cone are
elliptically polarized, with major axis locked to the direction of exciton
velocity, and helicity specified by the valley indices of the electron and the
hole. These finite-velocity light cones allow unprecedented possibilities to
optically inject valley polarization and valley current, and the observation of
both direct and inverse valley Hall effects, by exciting interlayer excitons.
Our findings suggest potential excitonic circuits with valley functionalities,
and unique opportunities to study exciton dynamics and condensation phenomena
in semiconducting 2D heterostructures.
