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arXiv · 1604.03297

Ultrafast non-thermal laser excitation of gigahertz longitudinal and shear acoustic waves in spin-crossover molecular crystals [$Fe(PM-AzA)_{2}$$(NCS)_{2}$]

T. Parpiiev·M. Servol·M. Lorenc·I. Chaban·E. Collet·H. Cailleau·P. Ruello·G. Chastanet·T. Pezeril
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Abstract

We report GHz longitudinal as well as shear acoustic phonons photoexcitation and photodetection using femtosecond laser pulses in a spin-crossover molecular crystal. From our experimental observation of time domain Brillouin scattering triggered by the photoexcitation of acoustic waves across the low-spin (LS) to high-spin (HS) thermal crossover, we reveal a link between molecular spin state and photoexcitation of coherent GHz acoustic phonons. In particular, we experimentally evidence an unconventional non-thermal pathway for the laser excitation of GHz phonons. We also provide experimental insight on the optical and mechanical parameters evolution across the LS/HS spin crossover temperature T$_{1/2}$.

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T. Parpiiev, M. Servol, M. Lorenc, I. Chaban, E. Collet, H. Cailleau, P. Ruello, G. Chastanet, T. Pezeril. 2016-04-12. Ultrafast non-thermal laser excitation of gigahertz longitudinal and shear acoustic waves in spin-crossover molecular crystals [$Fe(PM-AzA)_{2}$$(NCS)_{2}$]. https://doi.org/10.1063/1.5009657

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