Dielectrics in a time-dependent electric field: a real-time approach based on density-polarization functional theory

TL;DR

This paper introduces a real-time density-polarization functional theory approach to model dielectric responses under time-dependent electric fields, capturing long-range correlations and nonlinear optical phenomena.

Contribution

It proposes a novel real-time formalism using density and polarization as key variables, effectively describing dielectric dynamics beyond traditional density-only methods.

Findings

Accurately models optical absorption and harmonic generation in semiconductors.

Demonstrates the importance of polarization in capturing long-range correlations.

Links with advanced exchange-correlation functional approximations.

Abstract

In the presence of a (time-dependent) macroscopic electric field the electron dynamics of dielectrics cannot be described by the time-dependent density only. We present a real-time formalism that has the density and the macroscopic polarization P as key quantities. We show that a simple local function of P already captures long-range correlation in linear and nonlinear optical response functions. Specifically, after detailing the numerical implementation, we examine the optical absorption, the second- and third-harmonic generation of bulk Si, GaAs, AlAs and CdTe at different level of approximation. We highlight links with ultranonlocal exchange-correlation functional approximations proposed within linear response time-dependent density functional theory framework.