Exciton-plasmon states in nanoscale materials: breakdown of the Tamm-Dancoff approximation

TL;DR

This paper demonstrates that the Tamm-Dancoff approximation fails to accurately describe exciton-plasmon hybrid states in nanoscale materials, and proposes a new method that correctly captures these complex interactions.

Contribution

The authors introduce a novel approach that overcomes the limitations of the Tamm-Dancoff approximation in modeling exciton-plasmon states in nanoscale systems.

Findings

Tamm-Dancoff approximation can produce significant errors in nanoscale exciton-plasmon modeling.

Exciton-plasmon hybridization involves oscillations of electron-hole pairs in both directions in time.

The proposed method accurately describes excitons, plasmons, and their hybrid states.

Abstract

Within the Tamm-Dancoff approximation ab initio approaches describe excitons as packets of electron-hole pairs propagating only forward in time. However, we show that in nanoscale materials excitons and plasmons hybridize, creating exciton--plasmon states where the electron-hole pairs oscillate back and forth in time. Then, as exemplified by the trans-azobenzene molecule and carbon nanotubes, the Tamm-Dancoff approximation yields errors as large as the accuracy claimed in ab initio calculations. Instead, we propose a general and efficient approach that avoids the Tamm--Dancoff approximation, and correctly describes excitons, plasmons and exciton-plasmon states.