Strong-field effects in the photo-emission spectrum of the C$_{60}$ fullerene

TL;DR

This study uses advanced simulations to analyze strong-field photo-emission from C$_{60}$ fullerene, revealing highly collimated high-energy electron beams aligned with laser polarization and interference effects shaping the spectrum.

Contribution

It demonstrates the strong collimation of high-energy electrons and links spectral features to intracycle and intercycle interferences using time-dependent density functional theory.

Findings

High-energy electrons are strongly collimated along the laser polarization axis.

The high-energy plateau cut-off matches classical three-step model estimates.

Interference effects modulate the high-energy part of the spectrum.

Abstract

Considering C$_{60}$ as a model system for describing field emission from the extremity of a carbon nanotip, we explore electron emission from this fullerene excited by an intense, near-infrared, few-cycle laser pulse ($10^{13}$-$10^{14}~{\rm W/cm}^2$, 912 nm, 8-cycle). To this end, we use time-dependent density functional theory augmented by a self-interaction correction. The ionic background of C$_{60}$ is described by a soft jellium model. Particular attention is paid to the high energy electrons. Comparing the spectra at different emission angles, we find that, as a major result of this study, the photoelectrons are strongly peaked along the laser polarization axis forming a highly collimated electron beam in the forward direction, especially for the high energy electrons. Moreover, the high-energy plateau cut-off found in the simulations agrees well with estimates from the classical three-step model. We also investigate the build-up of the high-energy part of a photoelectron spectrum by a time-resolved analysis. In particular, the modulation on the plateau can be interpreted as contributions from intracycle and intercycle interferences.