Fig. 2: Comparison of transport behaviors for devices obtained by different fabrication methods.

a Transport behaviors at CNP for a 7-SL device without AlO_x covering layer. Due to fabrication effects, the surface state shifts down to the second SL (inset), and the hysteresis of σ_xy near zero field almost disappears. b Variation of σ_xy and σ_xx as a function of V_g at μ₀H = −8 T and 0, respectively. The black dashed line represents the V_g window where σ_xy plateaus coexist under zero and high μ₀H conditions, respectively. c Transport behavior of a 7-SL device exfoliated from a MnBi₂Te₄ flake on the same tape, but with an AlO_x layer deposited during the fabrication process. The large hysteresis indicates excellent protection of device performance. The inset illustrates that the topological surface state remains predominantly distributed on the outermost surface due to the protection of AlO_x. d In the same V_g range of high field Chern insulator state (marked by black dashed line), σ_xy at μ₀H = 0 exhibits a broad plateau during sweeping V_g. e, f μ₀H-dependent σ_xy at T = 1.5 K for 17 odd-SL devices. The only difference during their fabrication lies in whether the surface was deposited with AlO_x. All the devices exhibit quantized σ_xy at high μ₀H, as marked by the black dashed lines. g Summarized σ_xy at μ₀H = 0 and ∆σ_xy/∆H values at the plateau transition for the 17 devices. Devices with AlO_x capping layer (blue) generally show a larger AH effect than those without AlO_x (red). The inset displays the histograms of AH effect distribution of the 17 devices. The size of each bin on the σ_xy-axis is 0.1 e²/h.