Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Nat Commun. 2013;4:1468. doi: 10.1038/ncomms2480.
Fundamental interactions induced by lattice vibrations on ultrafast time scales have become increasingly important for modern nanoscience and technology. Experimental access to the physical properties of acoustic phonons in the terahertz-frequency range and over the entire Brillouin zone is crucial for understanding electric and thermal transport in solids and their compounds. Here we report on the generation and nonlinear propagation of giant (1 per cent) acoustic strain pulses in hybrid gold/cobalt bilayer structures probed with ultrafast surface plasmon interferometry. This new technique allows for unambiguous characterization of arbitrary ultrafast acoustic transients. The giant acoustic pulses experience substantial nonlinear reshaping after a propagation distance of only 100 nm in a crystalline gold layer. Excellent agreement with the Korteveg-de Vries model points to future quantitative nonlinear femtosecond terahertz-ultrasonics at the nano-scale in metals at room temperature.
晶格振动在超快时间尺度上引起的基本相互作用，对于现代纳米科学和技术变得越来越重要。在太赫兹频率范围内和整个布里渊区中，实验获得声子的物理性质对于理解固体及其化合物中的电输运和热输运至关重要。在这里，我们报告了在金/钴双层结构中通过超快表面等离激元干涉测量产生和非线性传播的巨大（1%）声应变脉冲。这项新技术允许对任意超快声瞬变进行明确的表征。在晶体金层中传播仅 100nm 后，巨大的声脉冲经历了显著的非线性重塑。与 Korteweg-de Vries 模型的极好一致性表明，未来在室温下的金属中，纳米尺度的定量非线性飞秒太赫兹超声将成为可能。
