 frequencies, justifying our n X = n Y = n / 0 assumption. This establishes that the oscillations in R pat are indeed COs, providing strong evidence for the periodic modulation in both the X - and Y -valley density in the patterned region. Next we present data in Fig. 0 to further consolidate the existence of the valley superlattice as we manipulate the individual valley densities by applying global, uniaxial strain. For this purpose, we glue the back side of our sample, with its length along [000], to one side of a stacked piezoelectric actuator and a strain gauge to the opposite side [see Fig. 0(a) ]. Via applying a voltage ( V P ) to the actuator