X-ray Dichroism in Noncetrosymmetric crystals

In this paper the authors analyse near-edge absorption of x rays in noncentrosymmetric crystals. The work is motivated by recent observations of x-ray dichroic effects which stems from parity-nonconserving electron interactions. We provide a theoretical description of these experiments and show that they are sensitive to microscopic {\it polar} and {\it magnetoelectric} properties of the sample. Our derivation extends previous theoretical work on centrosymmetric systems and identifies new directions in the microscopic analysis of crystalline materials using x-ray absorption spectroscopy.