ESRF Highlights 2021

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7 1 I H I G H L I G H T S 2 0 2 1

PRINCIPAL PUBLICATION AND AUTHORS

Strain Wave Pathway to Semiconductor-to-Metal Transition Revealed by Time-Resolved X-ray Powder Diffraction, C. Mariette (a,i), M. Lorenc (a), H. Cailleau (a), E. Collet (a), L. Guérin (a), A. Volte (a), E. Trzop (a), R. Bertoni (a), X. Dong (a), B. Lépine (a), O. Hernandez (b), E. Janod (c), L. Cario (c), V. Ta Phuoc (d), S. Ohkoshi (e), H. Tokoro (e,f), L. Patthey (g), A. Babic (g), I. Usov (g), D. Ozerov (g), L. Sala (g), S. Ebner (g), P. Böhler (g), A. Keller (g), A. Oggenfuss (g), T. Zmofing (g), S. Redford (g), S. Vetter (g), R. Follath (g), P. Juranic (g), A. Schreiber (g), P. Beaud (g), V. Esposito (g,) Y. Deng (g), G. Ingold (g), M. Chergui (h), G.F. Mancini (g,h), R. Mankowsky (g), C. Svetina (g), S. Zerdane (g), A. Mozzanica (g), A. Bosak (i), M. Wulff (i), M. Levantino (i), H. Lemke (g), M. Cammarata (a,i), Nat. Commun. 12, 1239 (2021); https:/doi.org/10.1038/s41467-021-21316-y (a) Univ. Rennes, CNRS, IPR (Institut de Physique de Rennes) - UMR 6251, Rennes (France) (b) Univ. Rennes, CNRS, ISCR (Institut des Sciences Chimiques de Rennes) - UMR 6226, Rennes (France) (c) Institut des Matériaux Jean Rouxel (IMN), Université de Nantes, CNRS, Nantes (France) (d) GREMAN UMR 7347 CNRS, Université de Tours, Tours (France) (e) Department of Chemistry, University of Tokyo (Japan) (f) Department of Materials Science, Faculty of Pure and Applied Sciences, University of Tsukuba, Ibaraki (Japan) (g) SwissFEL, Paul Scherrer Institut, Villigen (Switzerland) (h) Laboratory of Ultrafast Spectroscopy, Lausanne Center for Ultrafast Science (LACUS), École Polytechnique Fédérale de Lausanne, Lausanne (Switzerland) (i) ESRF

Fig. 56: Femtosecond XRD data revealing the build-up of local stress triggered by electronic excitation.

REFERENCES

[1] C. Thomsen et al., Phys. Rev. B 34, 4129-4138 (1986). [2] D Schick et al., Struct. Dyn. 1, 064501 (2014). [3] P. Ruello & V.E. Gusev, Ultrasonics 56, 21-35 (2015). [4] K.R. Tasca et al., Chem. Phys. Chem. 18, 1385 (2017). [5] A. Asahara et al., Phys. Rev. B 90, 014303 (2014).

are observed. Shear induces peak shifts within the first picoseconds. It can be that fast (and faster than volume) due to the domain structure of these crystals. Second, these local changes build up stress that generates strain waves propagating at the speed of sound and transforming the upper 100-nm-thick layer into a metal. In the third step, heat diffusion completes the transformation of the

bulk that was not exposed to the laser. The strain and phase transition propagate at the same velocity, which is much faster than thermal diffusion. The bulk transition is therefore driven by the strain wave. This non-destructive approach opens new perspectives for strain control of phase transitions in nanocrystallites that are excited by light.