▎ 摘　　要

The zero-energy Landau level of bilayer graphene is shown to be anomalously sharp (delta-function-like) against bond disorder as long as the disorder is correlated over a length scale exceeding a few lattice constants. The robustness of the zero-mode anomaly can be attributed to the preserved chiral symmetry. Unexpectedly, even when we apply a finite potential difference (i.e., an electric field) between the top and the bottom layers, the valley-split n = 0 Landau levels remain anomalously sharp, although they are now shifted away from the zero energy, while the n = 1 Landau levels exhibit the usual behavior.