The evolution of the bismuth crystal structure upon excitation of its A1g phonon has been intensely studied with short pulse optical lasers. Here we present the first-time observation of a hard x-ray induced ultrafast phase transition in a bismuth single crystal, at high intensities (~1014 W/cm2). The lattice evolution was followed using a recently demonstrated x-ray single-shot probing setup. The time evolution of the (111) Bragg peak intensity showed strong dependence on the excitation fluence. After exposure to a sufficiently intense x-ray pulse, the peak intensity dropped to zero within 300fs, i.e. faster than one oscillation period of the A1g mode at room temperature. Our analysis indicates a nonthermal origin of a lattice disordering process, and excludes interpretations based on electron-ion equilibration process, or on thermodynamic heating process leading to a plasma formation.
@article{arxiv.1807.06865,
title = {Femtosecond phase-transition in hard x-ray excited bismuth},
author = {M. Makita and I. Vartiainen and I. Mohacs and C. Caleman and A. Diaz and H. O. Jönsson and P. Juranić and N. Medvedev and A. Meents and A. Mozzanica and N. Opara and C. Padeste and V. Panneels and V. Saxena and M. Sikorski and S. Song and L. Vera and P. R. Willmott and P. Beaud and C. J. Milne and B. Ziaja-Motyka and C. David},
journal= {arXiv preprint arXiv:1807.06865},
year = {2018}
}
Comments
Main text 10 pages, 3 figures. Appendix 3 pages, 2 figures