Observation of Berry's Geometrical Phase in Electron Diffraction from a Screw Dislocation

The equations which govern high-energy electron diffraction in a deformed crystal lattice are shown to be equivalent to a Schr\"odinger equation with a time-dependent Hamiltonian. If the lattice planes are not strongly distorted, as in the long-ranged strain field of a dislocation, this time variation is slow and adiabatic theory can be used. The effects of Berry's geometrical phase are then observed in the bending of two-beam diffraction fringes as a screw dislocation is crossed.