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

作者：T. Parpiiev, Marina Servol, Maciej Lorenc, Ievgeniia Chaban, Ronan Lefort, Éric Collet, H. Cailleau, P. Ruello, Nathalie Daro, Guillaume Chastanet, Thomas Pézeril · 发表于：Applied Physics Letters · 年份：2017 · DOI：10.1063/1.4996538 · 被引用次数：12 · 研究领域：Magnetism in coordination complexes、Electron Spin Resonance Studies、Organic and Molecular Conductors Research

We report GHz longitudinal as well as shear acoustic phonon 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 the molecular spin state and photoexcitation of coherent GHz acoustic phonons. In particular, we experimentally evidence a non-thermal pathway for the laser excitation of GHz phonons. We also provide experimental insights into the optical and mechanical parameters evolving across the LS/HS spin crossover temperature range.