▎ 摘　　要

We study the effect of mechanical deformations on the electronic properties of hexagonal flakes of bilayer graphene. The behavior of electrons induced by triaxial strain can be described by an effective pseudo-magnetic field which is homogeneous in the center of the flake. We find that in-plane strain, applied to both layers equally, can break the layer symmetry leading to different behavior in the top and bottom layers of graphene. At low energy, just one of the layers feels the pseudo-magnetic field: the zero-energy pseudo-Landau level is missing in the second layer, thus creating a gap between the lowest non-zero levels. While the layer asymmetry is most significant at zero energy, interaction with the edges of the flake extends the effect to higher pseudo-Landau levels. The behavior of the top and bottom layers may be reversed by rotating the triaxial strain by 60 degrees. (C) 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim