Tuning chirality amplitude at ultrafast timescales in chiral CsCuCl3

Abstract

Chirality is a fundamental symmetry concept relevant to many scientific fields. It describes discrete states, i.e., left-handed, right-handed, or achiral. In contrast to this discrete classification, objects can be continuously distorted. To describe the deviation from an achiral state, the chirality amplitude has to be addressed, similarly to magnetization being the "amplitude"for time-reversal symmetry breaking. Even though symmetry breaking is the base for many phenomena in science in general, symmetry cannot quantitatively predict measurable quantities. Chirality amplitude is the key quantity for quantifying chirality-related emergent phenomena. Here, we propose two types of chiral lattice distortions and report their ultrafast dynamics. We determine the ultrafast reduction of the chirality amplitude in CsCuCl3 after an optical excitation by using resonant x-ray diffraction with circular polarization. An additional symmetry breaking representing a nonhanded chiral structure is observed by resonant x-ray diffraction when exciting the material with an intense, low-cycle terahertz pulse. The latter demonstrates a hidden enantiomorphic pair in a nonhanded chiral structure. The concept of chirality amplitude, as well as the decomposition into two different types of chiral lattice distortions, suggests a unique approach toward controlling chirality-induced emergent phenomena.