论文标题
时间分辨的X射线粉末衍射揭示的半导体到金属过渡的应变波途径
Strain Wave Pathway to Semiconductor-to-Metal Transition revealed by time resolved X-ray powder diffraction
论文作者
论文摘要
得益于超快科学的显着发展，当今的挑战之一是通过用轻脉冲控制连接两个不同阶段的相干运动来修改材料状态。在这里，我们展示了通过电子和结构前体现象发射的应变波如何确定半导体到金属过渡的宏观变换途径，并在Bistable ti $ _3 $ _3 $ _5 $ _5 $ nanocrystals中具有较大的体积变化。飞秒粉末X射线衍射使我们能够量化与相关时间尺度上相关的相变相关的结构变形。我们监测了吸收金属二聚体周围的早期内部扭曲，但还监视了在激光暴露的Ti $ _3 $ o $ $ _5 $表面的声波动态控制的长距离晶体变形。我们通过简化的弹性模型合理化了这些观察结果，表明宏观转化与Picsecond Timescale上的传播声波同时发生，比随后由热热扩散控制的热过程早几十年。
Thanks to the remarkable developments of ultrafast science, one of today's challenges is to modify material state by controlling with a light pulse the coherent motions that connect two different phases. Here we show how strain waves, launched by electronic and structural precursor phenomena, determine a macroscopic transformation pathway for the semiconducting-to-metal transition with large volume change in bistable Ti$_3$O$_5$ nanocrystals. Femtosecond powder X-ray diffraction allowed us to quantify the structural deformations associated with the photoinduced phase transition on relevant time scales. We monitored the early intra-cell distortions around absorbing metal dimers, but also long range crystalline deformations dynamically governed by acoustic waves launched at the laser-exposed Ti$_3$O$_5$ surface. We rationalize these observations with a simplified elastic model, demonstrating that a macroscopic transformation occurs concomitantly with the propagating acoustic wavefront on the picosecond timescale, several decades earlier than the subsequent thermal processes governed by heat diffusion.
