Ultrastrong Coupling of a Single Molecule to a Plasmonic Nanocavity: A First-Principles Study

Mikael Kuisma, Benjamin Rousseaux, Krzysztof M. Czajkowski, Tuomas P. Rossi, Timur Shegai, Paul Erhart, Tomasz J. Antosiewicz*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

17 Citations (Scopus)
57 Downloads (Pure)

Abstract

Ultrastrong coupling (USC) is a distinct regime of light-matter interaction in which the coupling strength is comparable to the resonance energy of the cavity or emitter. In the USC regime, common approximations to quantum optical Hamiltonians, such as the rotating wave approximation, break down as the ground state of the coupled system gains photonic character due to admixing of vacuum states with higher excited states, leading to ground-state energy changes. USC is usually achieved by collective coherent coupling of many quantum emitters to a single mode cavity, whereas USC with a single molecule remains challenging. Here, we show by time-dependent density functional theory (TDDFT) calculations that a single organic molecule can reach USC with a plasmonic dimer, consisting of a few hundred atoms. In this context, we discuss the capacity of TDDFT to represent strong coupling and its connection to the quantum optical Hamiltonian. We find that USC leads to appreciable ground-state energy modifications accounting for a non-negligible part of the total interaction energy, comparable to kBT at room temperature.

Original languageEnglish
Pages (from-to)1065-1077
Number of pages13
JournalACS Photonics
Volume9
Issue number3
Early online date2022
DOIs
Publication statusPublished - 16 Mar 2022
MoE publication typeA1 Journal article-refereed

Keywords

  • excitons
  • nanophotonics
  • plasmonics
  • strong coupling
  • time-dependent density functional theory

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  • PLASMOCAT: PLASMOCAT

    Rossi, T.

    01/09/202030/11/2022

    Project: Academy of Finland: Other research funding

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