Enabling the light-control of complex systems on ultra-short timescales gives rise to rich physics with promising applications. While crucial, the quantitative determination of both the longitudinal and shear photo-induced strains still remains challenging. Here, by scrutinizing asymmetric Bragg peaks pairs (±h01) using picosecond time-resolved X-ray diffraction experiments in BiFeO3, we simultaneously determine the longitudinal and shear strains. The relative amplitude of those strains can be explained only if both thermal and non-thermal processes contribute to the acoustic phonon photogeneration process. Importantly, we also reveal a difference of the dynamical response of the longitudinal strain with respect to the shear one due to an interplay of quasi-longitudinal and quasi-transverse acoustic modes, well reproduced by our model.
@article{arxiv.2007.10967,
title = {Ultrafast light-induced shear strain probed by time-resolved X-ray diffraction: the model multiferroic BiFeO$_3$ as a case study},
author = {V. Juvé and R. Gu and S. Gable and T. Maroutian and G. Vaudel and S. Matzen and N. Chigarev and S. Raetz and V. E. Gusev and M. Viret and A. Jarnac and C. Laulhé and A. Maznev and B. Dkhil and P. Ruello},
journal= {arXiv preprint arXiv:2007.10967},
year = {2021}
}