Non-chiral 1T-TiSe2 creates circular dichroism in resonant X-ray diffraction via multipole scattering interference

TL;DR

This paper reveals that non-chiral 1T-TiSe2 can produce circular dichroism in resonant X-ray diffraction through multipole scattering interference, challenging previous interpretations of chiral order.

Contribution

It demonstrates that interference between atomic multipoles can generate circular dichroism in non-chiral crystals, providing a new method to analyze multipole structures in RXD.

Findings

Reproduces experimental circular dichroism in 1T-TiSe2 with ab initio calculations.

Shows interference effects can mimic chirality in RXD signals.

Proposes a general approach to extract atomic multipoles from circular contrast.

Abstract

Resonant X-ray diffraction (RXD) provides a unique capability to investigate electronically ordered states in matter. Importantly, circular dichroism in RXD can determine the absolute chirality formed by anisotropic multipole arrangement. Here, we demonstrate that the scattering interference between distinct atomic electric multipoles can create circular contrast in resonant RXD even in a non-chiral crystal. These general considerations are applied to 1T-TiSe2, where recently reported circular dichroism in RXD was used to claim a chiral charge density wave order. We show that the experimental observations are well reproduced by our ab initio calculations based on the centrosymmetric crystal structure. Our results not only illuminate a way for a better understanding of possible chiral electronic order but also propose a general approach to extract buried high-order atomic multipoles via circular contrast in RXD. Besides, we discuss the difference in the circular dichroism of RXD originated by crystal chirality in chiral crystals and the interference effect in non-chiral crystals.