Fig. 3: Critical exponent in the QAH and insulating regimes.

a Current dependence of ρ_xx at various temperatures. All data are measured under a 1 T magnetic field. b Effective temperature T_e vs. Hall voltage V_yx. Under small currents, T_e equals the bath temperature. As the current increases, the electrons are dominantly thermalized by the electric field, and all data approach a universal curve (fitted by the black dashed lines) with a slope of 2/(p+2) = 0.49, yielding p = 2.08 in the QAH regime. c Temperature dependence of I_c. The breakdown current at a given temperature is defined as the current at which ρ_xx exceeds m times of ρ_xx measured at the base current, where m = 1.1 (red), 1.4 (blue), or 2 (green). The slope of the I_c vs. T curve in the log-log plot gives p = 2.14. d Temperature dependence of ρ_xx^max. The blue dots are obtained from the resistance maximum in the field-dependent ρ_xx curves measured at different temperatures and the cyan lines are extrapolated from the blue dots. e Current dependence of ρ_xx^max. f Effective temperature T_e vs. voltage V_xx^max, under large currents the slope in the log-log plot is 2/(p+2) = 0.48, yielding p = 2.17 in the insulating regime.