Photocurrent-induced harmonics in nanostructures

TL;DR

This paper demonstrates that photocurrent-induced harmonics in nanostructures arise from a mechanism similar to gases, influenced by local field gradients, providing insights into electron states in the continuum.

Contribution

It reveals that photocurrent-induced harmonics in nanostructures are driven by a mechanism akin to gases and explores how local field gradients affect these harmonics.

Findings

Harmonics in nanostructures originate from a gas-like mechanism.

Local field gradients significantly influence harmonic generation.

Insights into electron initial velocity in the continuum are provided.

Abstract

Photocurrent-induced harmonics appear in gases and solids due to tunnel ionization of electrons in strong fields and subsequent acceleration. In contrast to three-step harmonic emission, no return to the parent ions is necessary. Here we show that the same mechanism produces harmonics in metallic nanostructures in strong fields. Furthermore, we demonstrate how strong local field gradient, appearing as a consequence of the field enhancement, affects photocurrent-induced harmonics. This influence can shed light at the state of electron as it appears in the continuum, in particular, to its initial velocity.