▎ 摘　　要

The Fermi line of bilayer graphene at zero energy is transformed into four separated points positioned trigonally at the corner of the hexagonal first Brillouin zone. We show that as a result of this trigonal splitting the minimal conductivity of an undoped bilayer graphene strip becomes anisotropic with respect to the orientation theta of the connected electrodes and finds a dependence on its length L on the characteristic scale center dot=pi/Delta k similar or equal to 50 nm determined by the inverse of k-space distance of two Dirac points. The minimum conductivity increases from a universal isotropic value sigma(min)(perpendicular to)=(8/pi)e(2)/h for a short strip L