Ionization-Induced Subcycle Metallization of Nanoparticles in Few-Cycle Pulses
Qingcao Liu, Lennart Seiffert, Frederik Süßmann, Sergey Zherebtsov, Johannes Passig, A. R. Kessel, S. A. Trushin, Nora G. Kling, I. Ben-Itzhak, V. Mondes, Christina Gräf, E. Rühl, L. Veisz, S. Karsch, Jessica Rodríguez‐Fernández, Mark I. Stockman, J. Tiggesbäumker, K.‐H. Meiwes‐Broer, Thomas Fennel, Matthias F. Kling
Abstract
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.