Femtosecond phase-transition in hard x-ray excited bismuth

M. Makita; I. Vartiainen; I. Mohacs; C. Caleman; A. Diaz; H. O. Jönsson; P. Juranić; N. Medvedev; A. Meents; A. Mozzanica; N. Opara; C. Padeste; V. Panneels; V. Saxena; M. Sikorski; S. Song; L. Vera; P. R. Willmott; P. Beaud; C. J. Milne; B. Ziaja-Motyka; C. David

arXiv · 1807.06865

Femtosecond phase-transition in hard x-ray excited bismuth

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Abstract

The evolution of the bismuth crystal structure upon excitation of its A$_{1g}$ 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 (~$10^{14}$ W/cm$^2$). 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.

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M. Makita, I. Vartiainen, I. Mohacs, C. Caleman, A. Diaz, H. O. Jönsson, P. Juranić, N. Medvedev, A. Meents, A. Mozzanica, N. Opara, C. Padeste, V. Panneels, V. Saxena, M. Sikorski, S. Song, L. Vera, P. R. Willmott, P. Beaud, C. J. Milne, B. Ziaja-Motyka, C. David. 2018-07-18. Femtosecond phase-transition in hard x-ray excited bismuth. https://arxiv.org/abs/1807.06865

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