Strong-field laser-matter interactions in nanoscale targets offer unique avenues for the generation and detailed characterization of matter under extreme conditions. Field-driven, subcycle ionization-induced metallization of nanoscale solids in intense laser fields has been predicted (Peltz et al. Time-Resolved X-ray Imaging of Anisotropic Nanoplasma Expansion. Phys. Rev. Lett.2014, 113, 133401), but its observation was hampered by a lack of a smoking gun. Here, we report the ultrafast metallization of isolated dielectric and semiconducting nanoparticles under intense few-cycle laser pulses. The highest-energy electron emission is found to be a decisive proof that shows a characteristic cutoff modification to a metallic limit for intensities high enough to ignite carrier avalanching in the volume of the particles. Semiclassical Mean-field Mie Monte-Carlo transport simulations reveal the underlying dynamics and explain the observed evolution by near-field driven electron backscattering from the metallizing target.

中文翻译：

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少数循环脉冲中电离诱导的纳米粒子的亚循环金属化

纳米级目标中的强场激光物质相互作用为极端条件下物质的产生和详细表征提供了独特的途径。场驱动，在强激光领域纳米级固体的子周期电离诱导金属化已经预测（佩尔茨等各向异性Nanoplasma扩展的时间分辨X射线成像。物理评论快报。2014，113，133401），但是由于缺少抽烟枪而妨碍了它的观察。在这里，我们报告了在强烈的几个周期激光脉冲下，超快的隔离电介质和半导体纳米粒子的金属化。发现最高能量的电子发射是决定性的证明，其显示出对金属极限的特征性截止修饰，该极限对强度足够高以点燃粒子体积中的雪崩的载流子。半经典平均场Mie Monte-Carlo输运模拟揭示了潜在的动力学，并解释了近场驱动电子从金属化靶的反向散射观察到的演化。