Time-dependent density functional theory for strong electromagnetic fields in crystalline solids

TL;DR

This paper combines time-dependent density functional theory with Maxwell equations to study how intense laser pulses interact with crystalline silicon, revealing different response regimes and changes in reflectivity at various intensities.

Contribution

It introduces a coupled TDDFT-Maxwell approach to analyze strong-field laser interactions with crystalline solids, highlighting intensity-dependent optical responses.

Findings

Reflectivity decreases around 3×10^12 W/cm^2

Energy deposition reaches ~1 eV per atom at ~10^13 W/cm^2

Reflectivity increases significantly above 2×10^13 W/cm^2

Abstract

We apply the coupled dynamics of time-dependent density functional theory and Maxwell equations to the interaction of intense laser pulses with crystalline silicon. As a function of electromagnetic field intensity, we see several regions in the response. At the lowest intensities, the pulse is reflected and transmitted in accord with the dielectric response, and the characteristics of the energy deposition is consistent with two-photon absorption. The absorption process begins to deviate from that at laser intensities ~ 10^13 W/cm^2, where the energy deposited is of the order of 1 eV per atom. Changes in the reflectivity are seen as a function of intensity. When it passes a threshold of about 3 \times 1012 W/cm2, there is a small decrease. At higher intensities, above 2 \times 10^13 W/cm^2, the reflectivity increases strongly. This behavior can be understood qualitatively in a model treating the excited electron-hole pairs as a plasma.