Ionization-Induced Subcycle Metallization of Nanoparticles in Few-Cycle Pulses

作者：Liu, Qingcao; Seiffert, Lennart; Suessmann, Frederik; Zherebtsov, Sergey; Passig, Johannes; Kessel, Alexander; Trushin, Sergei A.; Kling, Nora G.; Ben-Itzhak, Itzik; Mondes, Valerie; Graf, Christina; Ruehl, Eckart; Veisz, Laszlo; Karsch, Stefan; Rodriguez-Fernandez, Jessica; Stockman, Mark, I; Tigge**aeumker, Josef; Meiwes-Broer, Karl-Heinz; Fennel, Thomas^*; Kling, Matthias F.^*

来源：ACS Photonics, 2020, 7(11): 3207-3215.

DOI：10.1021/acsphotonics.0c01282

• strong-field nanophysics
• avalanche ionization

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.