Effects of a non-causal electromagnetic response on the linear momentum transfer from a swift electron to a metallic nanoparticle

Abstract

Electron beams in Transmission Electron Microscopes (TEMs) can be used as a tool to induce movement on nanoparticles. Employing a classical-electrodynamics approach, it has been reported that the linear momentum transfer from a TEM-beam electron to a metallic spherical nanoparticle can be either attractive or repulsive towards the swift electron trajectory. However, these previous studies employed slow-convergence Newton-Cotes rules for numerical integration and a presumably non-causal electromagnetic response for the nanoparticle. Thus, a revision of these results is needed. In this theoretical work, we revise the calculations of the linear momentum transfer from a swift electron to a nanoparticle of radius of 1 nm, made of either aluminum or gold, studying the effects of non-causality and numerical convergence. Using an efficient numerical methodology, we found that poor numerical convergence, as well as non-causality, may lead to incorrect repulsive linear momentum transfer results. Contrary to what previous theoretical studies have suggested, our results show that the linear momentum transfer from a swift electron to the aluminum and gold nanoparticles is always attractive.