Giant Berry-phase-Driven X-Ray Beam Translations in Strain-Engineered Semiconductor Crystals

The manipulation of light through its interactions with artificially structured media is a cornerstone of photonics. The rescaling of this concept to the X-ray realm-which will enable us to control X-ray light with the same precision routinely available in the visible/IR range-has so far been hindered by the inherent difficulty of realizing photonic structures with the sub-nanometric resolution dictated by X-ray wavelengths. A promising approach to this challenge is based on the so-called Berry-phase effect, the large beam translations undergone by X-ray photons propagating in a deformed crystal, due to the simultaneous presence of Berry curvatures in real and reciprocal space. In this work, the controlled crystal distortions required to rein in this effect are obtained by pairing the lattice expansion observed upon H irradiation of GaAsN with a spatially selective hydrogenation technique. The macroscopic beam translations measured here are striking manifestations of the Berry curvatures associated with the sub-nanometric lattice distortions induced by H incorporation. Through the comparison with a dedicated theoretical model, the individual translation branches observed in X-ray transmission can be traced back to specific deformation features present within the samples, establishing a predictive framework for the control of X-ray propagation in the fabricated structures.