Extended Data Fig. 4: Additional transport measurements and removal of parasitic effects in the polarization measurements.

a, Conductance G versus V_b for the bilayer WTe₂ in device B2, measured with the top graphene grounded. The hysteresis occurs in exactly the same range of E_⊥ as it does in the graphene conductance in Fig. 2b. Note that both n_e and E_⊥ change when V_b is swept. The inset shows a schematic configuration of the measurement. b, Graphene conductance G_gr at 220 K as a function of V_b with the voltage V_W on the bilayer WTe₂ at 0 mV (blue) and 129 mV (red). The black curve is the difference between the blue and red curves. This subtraction removes most of the V_b dependence of the parasitic current that flows through the top graphene, which is not screened from the bottom gate by the WTe₂. Inset, graphene conductance showing the minimum at V_W = 129 mV.