Reformulation of Time-Dependent Density Functional Theory for Non-Perturbative Dynamics: The Rabi Oscillation Problem Resolved

TL;DR

This paper introduces a reformulation of TDDFT that accurately predicts non-perturbative dynamics like Rabi oscillations by using response quantities, overcoming previous limitations of the adiabatic approximation.

Contribution

A novel reformulation of TDDFT that enables accurate simulation of non-perturbative dynamics by relying on response functions instead of fully non-perturbative densities.

Findings

Successfully predicts Rabi oscillations in a model He atom

Accurately models charge-transfer in LiCN molecule

Reduces the failure of adiabatic approximation in TDDFT

Abstract

Rabi oscillations have long been thought to be out of reach in simulations using time-dependent density functional theory (TDDFT), a prominent symptom of the failure of the adiabatic approximation for non-perturbative dynamics. We present a reformulation of TDDFT which requires response quantities only, thus enabling an adiabatic approximation to predict such dynamics accurately because the functional is evaluated on a density close to the ground-state, instead of on the fully non-perturbative density. Our reformulation applies to it any real-time dynamics, redeeming TDDFT far from equilibrium. Examples of a resonantly-driven local excitation in a model He atom, and charge-transfer in the LiCN molecule are given.