Measuring excitation-energy transfer with a real-time time-dependent density functional theory approach

TL;DR

This paper presents a method to measure excitation-energy transfer times in molecular systems using a real-time TDDFT approach within an open quantum system framework, accounting for dissipation and defects.

Contribution

It introduces a novel real-time TDDFT-based approach combined with stochastic Schrödinger equations to study excitation transfer and dissipation in supermolecular systems.

Findings

Small deviations in electronic structure minimally affect transfer pathways.

Defects significantly slow down energy transfer.

The method captures dissipation effects via bath coupling.

Abstract

We investigate the time an electronic excitation travels in a supermolecular setup using a measurement process in an open quantum-system framework. The approach is based on the stochastic Schr\"odinger equation and uses a Hamiltonian from time-dependent density functional theory (TDDFT). It treats electronic-structure properties and intermolecular coupling on the level of TDDFT, while it opens a route to the description of dissipation and relaxation via a bath operator that couples to the dipole moment of the density. Within our study, we find that in supermolecular setups small deviations of the electronic structure from the perfectly resonant case have only minor influence on the pathways of excitation-energy transfer, thus lead to similar transfer times. Yet, sizable defects cause notable slowdown of the energy spread.