Observation of local chiral-symmetry breaking in globally centrosymmetric crystals

TL;DR

This paper demonstrates that anomalous x-ray resonant diffraction can detect chiral properties in centrosymmetric crystals, revealing local symmetry breaking through interference effects, supported by tensor analysis and ab initio simulations.

Contribution

It introduces a method to observe local chiral-symmetry breaking in globally centrosymmetric crystals using resonant diffraction and tensor analysis.

Findings

Access to chiral properties via interference in diffraction

Confirmation through ab initio numerical simulations

Ability to detect chiral quantities where dichroic techniques fail

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 $\alpha$-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.