Berry-Phase Translation of X Rays by a Deformed Crystal

We experimentally demonstrated an enhanced translation of an x-ray beam nearly parallel to the diffracting planes over millimeter distances in a deformed silicon crystal. This effect is a consequence of the Berry-phase effect in phase space [K. Sawada et al., Phys. Rev. Lett. 96, 154802 (2006)], which enables an interplay between the gap in the dispersion surface in momentum space and the atomic displacements in real space. Such an interplay in phase space enhances the beam translation by some 5 orders of magnitude, leading to the macroscopic effect.