# Comment on "Chiral Phase Transition in Charge Ordered 1T-TiSe2" and Supplementary Material on "First-order Forbidden X-ray Diffraction"

## TL;DR

This paper refutes previous claims of a chiral phase transition in TiSe2 based on x-ray diffraction data, demonstrating that there is only one achiral transition instead of multiple transitions.

## Contribution

It critically reanalyzes prior x-ray diffraction evidence, showing that the supposed chiral transition in TiSe2 does not exist, clarifying the nature of its phase transition.

## Key findings

- Prior evidence for chiral transition is incorrect
- There is only one achiral phase transition in TiSe2
- Previous modeling assumptions are invalid

## Abstract

A prior report of the emergence of chirality for the (2x2x2) charge density wave (CDW) in TiSe2 has attracted much interest; the drastic symmetry breaking is highly unusual with few precedents [1]. In that study, key evidence was provided by x-ray diffraction measurements of two superlattice reflections, (1.5 1.5 0.5) and (2.5 1 0). The (2.5 1 0) reflection appeared to show an anomalously large intensity and a transition onset at ~7 K below that of the (1.5 1.5 0.5) reflection. These observations, aided by modeling, were cited as evidence for a separate chiral transition. In this Comment, we show that the prior conclusions based on x-ray diffraction are erroneous. There is just one transition, and it is achiral.

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Source: https://tomesphere.com/paper/1903.11120