Fig. 4

a Size-independent four-terminal resistance R _xx measurement of bilayer graphene as a function of magnetic field at temperature 2 K. Resistance plateau is recorded in the R-H curve. This effect originates from an augmented sublattice spin-splitting due to the high surface-impurity concentration on the graphene layer. The derivative of the resistance curve shown in the bottom right corner inset clearly capture the resistance plateau at ~2.5, 3.5, 4.2, 6, 7.5, 8.9, 9.5, and 11.5 T. b The observed four-terminal resistance nonlinear increase with a magnetic field strength of the different temperature. The dotted line is fitted following the reported that this gap is of excitonic nature and to increase with \( \sqrt{B} \). The symbols present the measured data, and the lines are fitted