Non-adiabatic ponderomotive effects in photoemission from nanotips in intense mid-infrared laser fields

• Published in: arXiv.org
• Main Authors: Schötz, Johannes, Mitra, Sambit, Fuest, Harald, H, Neuhaus, Marcel, Okell, William A, ster, Michael, Paschen, Timo, Ciappina, Marcelo F, Yanagisawa, Hirofumi, Wnuk, Pawel, Hommelhoff, Peter, Kling, Matthias F
• Format: Paper
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 15.05.2019
• Subjects: Adiabatic flow; Computer simulation; Electron emission; Electron pulses; Emission analysis; Energy spectra; Gold; Infrared lasers; Kinetic energy; Lasers; Mathematical models; Near fields; Photoelectric emission
• ISSN: 2331-8422

Transient near-fields around metallic nanotips drive many applications, including the generation of ultrafast electron pulses and their use in electron microscopy. We have investigated the electron emission from a gold nanotip driven by mid-infrared few-cycle laser pulses. We identify a low-energy peak in the kinetic energy spectrum and study its shift to higher energies with increasing laser intensities from \(1.7\) to \(3.7\cdot10^{11} \mathrm{W}/\mathrm{cm}^2\). The experimental observation of the upshift of the low-energy peak is compared to a simple model and numerical simulations, which show that the decay of the near-field on a nanometer scale results in non-adiabatic transfer of the ponderomotive potential to the kinetic energy of emitted electrons and in turn to a shift of the peak. We derive an analytic expression for the non-adiabatic ponderomotive shift, which, after the previously found quenching of the quiver motion, completes the understanding of the role of inhomogeneous fields in strong-field photoemission from nanostructures.