Fig. 1: Basic properties of a 7-SL MnBi₂Te₄.

a Schematic crystal and magnetic structures of the 7-SL MnBi₂Te₄ device. b Configurations of chiral edge state in the Chern insulator with Chern number C = −1 and +1. The opposite chirality of the edge state is marked by red and blue lines with arrows. The magenta arrows denote the magnetic moments. The schematic electronic structures for the two cases are shown on the right, with the opposite slope of the linear band representing opposite chirality. c Optical image of Device #7-SL-1 and the measurement setup. d Magnetic field dependent R_xx (red) and R_yx (blue) at V_g = 4 V and T = 2 K. The Chern insulator phase is realized when the magnetic field is above 8 T, which is characterized by the R_yx = −h/e² plateau and R_xx = 0. e As V_g is tuned to −16 V, the transport is dominated by hole-type carriers. The jumps in R_xx at a magnetic field of around 1.8 T, 4 T, and 7 T correspond to the successive flips of Mn²⁺ moments in different SLs. f At V_g = 16 V, the E_F is tuned to the conduction band and the transport exhibits characteristic features of the 2D electron gas. The insets in d to f roughly show the position of E_F at according V_g.