Metal nanofilm in strong ultrafast optical fields

TL;DR

This paper predicts ultrafast optical field-induced transitions in metal nanofilms leading to semimetal-like states, with significant changes in reflectivity and transmissivity, relevant for nanoplasmonic and ultrafast electronic applications.

Contribution

It introduces a theoretical prediction of ultrafast semimetal-like state formation in metal nanofilms under high-field ultrashort pulses, revealing novel optical and electronic behaviors.

Findings

Reflectivity greatly reduced under high fields

Transmissivity and internal fields increased

Subcycle oscillations due to Bloch oscillations

Abstract

We predict that a metal nanofilm subjected to an ultrashort (single oscillation) optical pulse of a high field amplitude $\sim 3 \mathrm{V/\AA}$ at normal incidence undergoes an ultrafast (at subcycle times $\lesssim 1 \mathrm{fs}$) transition to a state resembling semimetal. Its reflectivity is greatly reduced, while the transmissivity and the optical field inside the metal are greatly increased. The temporal profiles of the optical fields are predicted to exhibit pronounced subcycle oscillations, which are attributed to the Bloch oscillations and formation of the Wannier-Stark ladder of electronic states. The reflected, transmitted, and inside-the-metal pulses have non-zero areas approaching half-cycle pulses. The effects predicted are promising for applications to nanoplasmonic modulators and field-effect transistors with petahertz bandwidth.