Figure 2

Hall conductivity σ_xy measured at B fields from 2 T to 10 T with a step of 0.10 T in (a) electron and (b) hole doping regimes. The blue arrows (green arrows) indicate the disappearance (reappearance) of the QH signatures. At ν_tot = 28, QH plateau disappears (orange arrow) and reappears (red arrow) with variation of total charge density n_tot. (c) Schematic illustration of band alignment diagram for twisted bilayer graphene. Upper and lower panels describe the cases with zero and a finite gate voltage V_g, respectively. Due to the residual charge density, residual electric field, eV_res, is induced even at V_g = 0 as illustrated in the magnified right inset of the upper pannel. (d) Calculated carrier densities n_U and n_L for the upper (navy) and the lower (dark cyan) layers with variation of n_tot at B = 10 T. The dot lines correspond to the carrier densities of each layer at zero magnetic field. For comparison, experimentally measured n_U (navy square) and n_L (dark cyan square) from Shubnikov-de Hass oscillations are plotted together. The inset shows the displacement field (D) due to carrier imbalance between the layers as a function of n_tot at B = 10 T (solid line) and 0 T (dashed line). Colour rendition of R_xx as function of the total filling factor, ν_tot for (e) D1 and (f) D2. The lines represent the calculated position of the Landau levels from each layer (see the text).