Speaker
Description
Control of light-matter interaction in quantum materials offers a pathway to access non-equilibrium states with emergent functionalities beyond thermal equilibrium [1, 2]. In strongly correlated systems, particularly those involving large volume changes associated or not to a symmetry breaking, ultrafast laser excitation can drive phase transitions [3, 4]. Recent work [5] further highlights the effect of nanoscopic morphology on the mechanism of macroscopic transformation as well as relaxation dynamics.
In this work, we investigate a geometry controlled strain wave dynamics during photoinduced phase transition in morphologically tailored single crystals of V2O3, a prototypical strongly correlated system. Using time-resolved X-ray diffraction and ultrafast optical reflectivity, we track the coupled structural and electronic dynamics during such a transition.
We identify a multistep process after laser excitation, starting with an initial monoclinic-to-hexagonal inverse ferroelastic transition, within ~ 10 ps. At several tens of ps, the propagation of a unidirectional and coherent strain wave perpendicular to the large surface hit by the ultrafast laser induces a symmetry-lowered state with intermediate volume, stabilising a transient monoclinic metallic phase - a long sought missing link in the V2O3 phase diagram. At longer delays, additional strain waves propagating in-plane drive the system towards the hexagonal phase, with dynamics governed by the speed of acoustic propagation and the crystal lateral size. These results demonstrate that the strain wave mechanism can act as a dynamical symmetry-breaking field enabling control of photoinduced transition pathways and access to emergent phases.
References:
[1] Koshihara, S. et al. Physics Reports 942, 1 (2022)
[2] Zhang, J. & Averitt, R. D. Annual Review of Materials Research 44, 19 (2014)
[3] Amano, T. et al. Nature Physics 20, 1778 (2024)
[4] Mariette, C. et al. Nature communications 12, 1239 (2021)
[5] Mandal, R. et al. Communications Materials 6, 209 (2025)