 smaller effective mass ( m t ) and higher mobility along the current direction ([000]). We remark that the saturating behavior of resistance at large | ϵ | is consistent with the green and red shaded regions, expected for the only- X - or only- Y -valley occupation in the 0DES, according to previous measurements [00,00] . 0 00.0000/PhysRevLett.000.000000.f0 FIG. 0. (a) Schematic of the experimental setup for the application of global, uniaxial strain ( ϵ ) with the sample and a strain gauge glued to the opposite faces of a piezoactuator. (b) Piezoresistance of the patterned region as a function of ϵ for n ≃ 0.0 × 00 00 cm - 0 . We mark points A - E on the trace. (c) Magnetoresistance traces corresponding to points A - E in (b). The traces are vertically offset for clarity. Arrows mark the prominent CO minima observed in the black traces. At higher fields, Shubnikov-de Haas oscillations, originating from the formation of well-defined Landau levels, are observed. (d) Schematic of the spatial density profile of the X and Y valleys for points A - E . Note that the density distributions shown are only qualitative. (e) Examples of FT spectra for different strain values. (f) Plot of the observed FT frequencies squared versus ϵ . The dashed green and red lines represent the expected ϵ -induced evolution of the CO frequencies from the X and Y valleys, respectively, for n ≃ 0.0 × 00 00 cm - 0 . In Fig. 0(c) , we show a series of low- B ⊥ magnetoresistance traces corresponding to points A − E in Fig. 0(b) . At ϵ = 0 (point C ), R pat manifests pronounced CO minima, as previously addressed in Fig. 0(e) . For moderate negative ϵ (point D ), the minima (marked by vertical arrows) move out to higher B ⊥ , expected for the growing X -valley population which increases k F , X . However, for point E , when the 0DES is completely valley polarized (only X ) at large ϵ < 0 , the COs disappear and instead strong Shubnikov-de Haas oscillations are seen. Much like the ϵ < 0 case, the COs are present (vertical arrows) only at moderate positive ϵ but not at large ϵ > 0 (point A ) when the 0DES is once again fully valley polarized (only Y ) [see the top trace in Fig. 0(c) ]. Note that if any residual piezoelectric effect were present along [000], it should modulate the total density even in the fully valley-polarized 0DES and give rise to COs. The absence of COs for the only- X or - Y cases therefore unambiguously rules out the existence of a piezoelectric effect along [000], as expected [00,00] . This also reaffirms that the observed COs are indeed made possible by the valley superlattice, which exists only in the bivalley cases, i.e., when both the X and Y valleys are occupied (points B − D ). Figure 0(d) further elucidates how the valley modulation (present in the bivalley cases) from the local strain field evolves under increasing global ϵ from the piezoactuator and is eventually nullified when large | ϵ | fully valley polarizes the entire 0DES. Figures 0(e) and 0(f) present a more quantitative picture of how each valley contributes to the COs as a function of ϵ . In Fig. 0(e) , we show FT spectra at a few representative strains. We plot these CO frequencies squared as a function of ϵ in Fig. 0(f) . The dashed green and red lines are based on the expressions f CO , Y 0 = h 0 m l / m t ( n + Δ n ) / π e 0 a 0 and f CO , X 0 = h 0 m t / m l ( n - Δ n ) / π e 0 a 0 , where f CO , Y and f CO , X are the expected CO frequencies for the Y and X valleys at a given Δ n ( = n Y - n X ), the density difference between the two valleys [00] . Here we convert Δ n to ϵ according to their empirical relation for n ≃ 0.0 × 00 00 cm - 0 , as reported in Ref. [00] , and the dashed lines are based on the relation f CO = 0 ℏ k F / e a [00] . As more electrons are transferred from the X to the Y valley with increasing ϵ [see Fig. 0(d) ], k F , X shrinks and thereby f CO , X decreases. In contrast, f CO , Y increases, since k F , Y gets enhanced. As seen in Fig. 0(f) , the COs