Onset of space-charge effects in strong-field photocurrents from nanometric needle tips

TL;DR

This paper investigates how space-charge effects influence strong-field photoemission from nanometric tungsten tips, revealing a threshold intensity where charge interactions dominate electron emission dynamics, with implications for ultrafast optoelectronic devices.

Contribution

The study identifies the onset of space-charge effects in nanostructure photoemission under intense laser fields through combined experiments and simulations, advancing understanding of charge interactions in ultrafast electron emission.

Findings

Step-wise increase in cutoff energies beyond a certain intensity.

Identification of charge-interaction dominated emission regime.

Relevance to nanostructure-based PHz-scale optoelectronic devices.

Abstract

Strong-field photoemission from nanostructures and the associated temporally modulated currents play a key role in the development of ultrafast vacuum optoelectronics. Optical light fields could push their operation bandwidth into the petahertz domain. A critical aspect for their functionality in the context of applications is the role of charge interactions, including space charge effects. Here, we investigated the photoemission and photocurrents from nanometric tungsten needle tips exposed to carrier-envelope phase-controlled few-cycle laser fields. We report a characteristic step-wise increase in the intensity-rescaled cutoff energies of emitted electrons beyond a certain intensity value. By comparison with simulations, we identify this feature as the onset of charge-interaction dominated photoemission dynamics. Our results are anticipated to be relevant also for the strong-field photoemission from other nanostructures, including photoemission from plasmonic nano-bowtie antennas used in carrier-envelope phase-detection and for PHz-scale devices.