Observation of local chiral-symmetry breaking in globally centrosymmetric crystals

Abstract

A thorough tensor analysis of the Bragg-forbidden reflection (00.3)$_h$ in corundum systems having a global center of inversion, like V$_2$O$_3$ and $α$-Fe$_2$O$_3$, shows that anomalous x-ray resonant diffraction can access chiral properties related to the dipole-quadrupole (E1-E2) channel via an interference with the pure quadrupole-quadrupole (E2-E2) process. This is also confirmed by independent {\it ab initio} numerical simulations. In such a way it becomes possible, in this particular case, to estimate the intensity of the ``twisted'' trigonal crystal field ($C_3$ symmetry) and, in general, to detect chiral quantities in systems where dichroic absorption techniques are ineffective.