Probing ultrafast symmetry breaking in photo-stimulated matter

TL;DR

This study uses picosecond Raman scattering to investigate ultrafast, non-thermal phase transitions in photo-stimulated Antimony, revealing a lower symmetry transition pathway contrary to traditional expectations.

Contribution

It demonstrates the application of ultrafast Raman scattering to analyze symmetry changes during non-thermal phase transitions in materials.

Findings

Evidence of an ultrafast reversible structural phase transition.

Transition evolves toward a lower symmetry, contrary to common models.

Feasibility of ultrafast Raman symmetry analysis for transient phases.

Abstract

The nature of a phase transition is inherently connected to the changes in the crystalline symmtry, which is typically probed by elastic or inelastic scattering with neutrons, electrons or photons. When such a phase transition is stimulated by light or other sudden perturbations the solid evolves along a non-equilibrium pathway of which the underlying physics is poorly understood. Here we use picosecond Raman scattering to study the photo-induced ultrafast dynamics in Peierls distorted Antimony. We find evidence for an ultrafast non-thermal reversible structural phase transition. Most surprisingly, we find evidence that this transition evolves toward a lower symmetry, in contrast to the commonly accepted rhombohedral-to-simple cubic transition path. Our study demonstrates the feasibility of ultrafast Raman scattering symmetry analysis of photo-induced non-thermal transient phases.