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Elastically driven cooperative response of a molecular material impacted by a laser pulse


Photoinduced phase transformations1,2 occur when a laser pulse impacts a material, thereby transforming its electronic and/or structural orders, consequently affecting the functionalities3,4,5,6,7. The transient nature of photoinduced states has thus far severely limited the scope of applications. It is of paramount importance to explore whether structural feedback during the solid deformation has the capacity to amplify and stabilize photoinduced transformations. Contrary to coherent optical phonons, which have long been under scrutiny8,9,10, coherently propagating cell deformations over acoustic timescales11,12,13,14 have not been explored to a similar degree, particularly with respect to cooperative elastic interactions. Herein we demonstrate, experimentally and theoretically, a self-amplified responsiveness in a spin-crossover material15 during its delayed volume expansion. The cooperative response at the material scale prevails above a threshold excitation, significantly extending the lifetime of photoinduced states. Such elastically driven cooperativity triggered by a light pulse offers an efficient route towards the generation and stabilization of photoinduced phases in many volume-changing materials.

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Figure 1: Response to femtosecond laser excitation of LS crystals of different sizes.
Figure 2: Photoresponse of nanocrystals to excitation density.
Figure 3: Monte Carlo simulations with the mechanoelastic model.
Figure 4: Schematics of the mechanism.


  1. 1

    Nasu, K. Photoinduced Phase Transitions (World Scientific, 2004).

    Book  Google Scholar 

  2. 2

    Cailleau, H. et al. Impacting materials by light and seeing their structural dynamics. Eur. Phys. J. 222, 1077–1092 (2013).

    Google Scholar 

  3. 3

    Ichikawa, H. et al. Transient photoinduced ‘hidden’ phase in a manganite. Nature Mater. 10, 101–105 (2011).

    CAS  Article  Google Scholar 

  4. 4

    Gao, M. et al. Mapping molecular motions leading to charge delocalization with ultrabright electrons. Nature 496, 343–346 (2013).

    CAS  Article  Google Scholar 

  5. 5

    Porer, M. et al. Non-thermal separation of electronic and structural orders in a persisting charge density wave. Nature Mater. 13, 857–861 (2014).

    CAS  Article  Google Scholar 

  6. 6

    Beaud, P. et al. A time-dependent order parameter for ultrafast photoinduced phase transitions. Nature Mater. 13, 923–927 (2014).

    CAS  Article  Google Scholar 

  7. 7

    Collet, E. et al. Laser-induced ferroelectric structural order in an organic charge-transfer crystal. Science 300, 612–615 (2003).

    CAS  Article  Google Scholar 

  8. 8

    Sokolowski-Tinten, K. et al. Femtosecond X-ray measurement of coherent lattice vibrations near the Lindemann stability limit. Nature 422, 287–289 (2003).

    CAS  Article  Google Scholar 

  9. 9

    Wall, S. et al. Ultrafast changes in lattice symmetry probed by coherent phonons. Nature Commun. 3, 721 (2012).

    CAS  Article  Google Scholar 

  10. 10

    Cammarata, M. et al. Sequential activation of molecular breathing and bending during spin-crossover photoswitching revealed by femtosecond optical and X-ray absorption spectroscopy. Phys. Rev. Lett. 113, 227402 (2014).

    Article  Google Scholar 

  11. 11

    Feurer, T., Vaughan, J. C. & Nelson, K. A. Spatiotemporal coherent control of lattice vibrational waves. Science 299, 374–377 (2003).

    CAS  Article  Google Scholar 

  12. 12

    Lejman, M. et al. Giant ultrafast photo-induced shear strain in ferroelectric BiFeO3 . Nature Commun. 5, 4301 (2014).

    CAS  Article  Google Scholar 

  13. 13

    Lorenc, M. et al. Cascading photoinduced, elastic, and thermal switching of spin states triggered by a femtosecond laser pulse in an Fe(III) molecular crystal. Phys. Rev. B 85, 054302 (2012).

    Article  Google Scholar 

  14. 14

    Collet, E. et al. Ultrafast spin-state photoswitching in a crystal and slower consecutive processes investigated by femtosecond optical spectroscopy and picosecond X-ray diffraction. Phys. Chem. Chem. Phys. 14, 6192–6199 (2012).

    Article  Google Scholar 

  15. 15

    Halcrow, M. (ed.) Spin-Crossover Materials (Wiley, 2013).

  16. 16

    Willenbacher, N. & Spiering, H. The elastic interaction of high-spin and low-spin complex molecules in spin-crossover compounds. J. Phys. C 21, 1423–1439 (1988).

    Article  Google Scholar 

  17. 17

    Bertoni, R., Lorenc, M., Tissot, A., Boillot, M.-L. & Collet, E. Femtosecond photoswitching dynamics and microsecond thermal conversion driven by laser heating in FeIII spin-crossover solids. Coord. Chem. Rev. 282–283, 66–76 (2015).

    Article  Google Scholar 

  18. 18

    Zhang, W. et al. Tracking excited-state charge and spin dynamics in iron coordination complexes. Nature 509, 345–348 (2014).

    CAS  Article  Google Scholar 

  19. 19

    Lorenc, M. et al. Successive dynamical steps of photoinduced switching of a molecular Fe(III) spin-crossover material by time-resolved x-ray diffraction. Phys. Rev. Lett. 103, 028301 (2009).

    CAS  Article  Google Scholar 

  20. 20

    Tissot, A., Bertoni, R., Collet, E., Toupet, L. & Boillot, M.-L. The cooperative spin-state transition of an iron(III) compound [FeIII(3-MeO-SalEen)2]PF6: thermal- vs ultra-fast photo-switching. J. Mat. Chem. 35, 2333–2340 (2011).

    Google Scholar 

  21. 21

    Félix, G. et al. Lattice dynamics in spin-crossover nanoparticles through nuclear inelastic scattering. Phys. Rev. B 91, 024422 (2015).

    Article  Google Scholar 

  22. 22

    Enachescu, C., Stoleriu, L., Stancu, A. & Hauser, A. Model for elastic relaxation phenomena in finite 2D hexagonal molecular lattices. Phys. Rev. Lett. 102, 257204 (2009).

    Article  Google Scholar 

  23. 23

    Tissot, A., Enachescu, C. & Boillot, M.-L. Control of the thermal hysteresis of the prototypal spin-transition FeII(phen)2(NCS)2 compound via the microcrystallites environment: experiments and mechanoelastic model. J. Mater. Chem. 22, 20451–20457 (2012).

    CAS  Article  Google Scholar 

  24. 24

    Stoleriu, L., Chakraborty, P., Hauser, A., Stancu, A. & Enachescu, C. Thermal hysteresis in spin-crossover compounds studied within the mechanoelastic model and its potential application to nanoparticles. Phys. Rev. B 84, 134102 (2011).

    Article  Google Scholar 

  25. 25

    Varret, F. et al. The propagation of the thermal spin transition of [Fe(btr)2(NCS)2]H2O single crystals, observed by optical microscopy. New J. Chem. 35, 2333–2340 (2011).

    CAS  Article  Google Scholar 

  26. 26

    Cobo, S. et al. Single-laser-shot-induced complete bidirectional spin transition at room temperature in single crystals of (FeII(pyrazine)(Pt(CN)4)). J. Am. Chem. Soc. 130, 9019–9024 (2008).

    CAS  Article  Google Scholar 

  27. 27

    Hauser, A., Gütlich, P. & Spiering, H. High-spin → low-spin relaxation kinetics and cooperative effects in the [Fe(ptz)6(BF4)2[Zn1−xFex(ptz)6](BF4)2 (ptz = 1-Propyltetrazole) spin-crossover systems. Inorg. Chem. 25, 4245–4248 (1986).

    CAS  Article  Google Scholar 

  28. 28

    Gütlich, P., Hauser, A. & Spiering, H. Thermal and optical switching of Iron (II) complexes. Angew. Chem. Int. Ed. 33, 2024–2054 (1994).

    Article  Google Scholar 

  29. 29

    Kobatake, S., Takami, S., Muto, H., Ishikawa, T. & Irie, M. Rapid and reversible shape changes of molecular crystals on photoirradiation. Nature 446, 778–781 (2007).

    CAS  Article  Google Scholar 

  30. 30

    Ohkoshi, S. et al. Synthesis of a metal oxide with a room-temperature photoreversible phase transition. Nature Chem. 2, 539–545 (2010).

    CAS  Article  Google Scholar 

  31. 31

    Camjayi, A. et al. First-order insulator-to-metal Mott transition in the paramagnetic 3D System GaTa4Se8 . Phys. Rev. Lett. 113, 086404 (2014).

    CAS  Article  Google Scholar 

  32. 32

    Veber, S. L. et al. High-field EPR reveals the strongly temperature-dependent exchange interaction in “breathing” crystals Cu(hfac)2LR. J. Am. Chem. Soc. 130, 2444–2445 (2008).

    CAS  Article  Google Scholar 

  33. 33

    Okamoto, H. et al. Photoinduced phase transition in tetrathiafulvalene-p-chloranil observed in femtosecond reflection spectroscopy. Phys. Rev. B 70, 165202 (2004).

    Article  Google Scholar 

  34. 34

    Okimoto, Y. et al. Ultrasonic propagation of a metallic domain in Pr0.5Ca0.5CoO3 undergoing a photoinduced insulator–metal transition. Phys. Rev. Lett. 103, 027402 (2009).

    CAS  Article  Google Scholar 

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This work was supported by the Institut Universitaire de France, Rennes Métropole, Région Bretagne (CREATE 4146), ANR (ANR-13-BS04-0002) and Europe (FEDER). C.E. thanks CNCS-UEFISCDI Romania (grant number PN-II-RU-TE-2014-4-0987).

Author information




E.C. and M.L. conceived and coordinated the project. R.B. performed time-resolved optical measurements and analysed the data. A.T., J.L. and M.-L.B. grew and prepared the samples. L.S., A.S. and C.E. extended the mechanoelastic model and performed Monte Carlo simulations. E.C., H.C., M.L., R.B. and C.E. proposed the physical picture and wrote the paper. All authors contributed to discussions and gave comments on the manuscript.

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Correspondence to Maciej Lorenc or Eric Collet.

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The authors declare no competing financial interests.

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Bertoni, R., Lorenc, M., Cailleau, H. et al. Elastically driven cooperative response of a molecular material impacted by a laser pulse. Nature Mater 15, 606–610 (2016).

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