▎ 摘　　要

We show nonlinear transport experiments on clean, suspended bilayer graphene that reveal a gap in the density of states. Looking at the evolution of the gap in magnetic fields of different orientation, we find that the ground state is a spin-ordered phase. Of the three possible gapped ground states that are predicted by theory for equal charge distribution between the layers, we can therefore exclude the quantum anomalous Hall phase, leaving the layer antiferromagnet and the quantum spin Hall phase as the only possible gapped ground states for bilayer graphene. DOI: 10.1103/PhysRevB.87.161402