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Approaching the quantum limit for plasmonics: linear atomic chains
1Quantum Measurement Division and Joint Quantum Institute, National Institute of Standards and Technology, Gaithersburg, MD, 20899-8423, USA; University of Maryland, College Park, MD 20742, USA.
Journal of Optics (2010)
|March 3, 2020
Summary
Developing a quantum theory for atomic-scale materials requires identifying optical excitations. This study reveals that many-body excitonic states, not typically found in density functional theory (DFT), dominate spectral responses in linear atomic chains.
Area of Science:
- Quantum mechanics
- Condensed matter physics
- Materials science
Background:
- Optical excitations in atomic-scale materials exhibit complex mixing of single-particle and collective responses.
- Quantifying these excitations is challenging due to the lack of clear quantization definitions.
- Linear atomic chains serve as ideal models for investigating collective excitations in nanoscale systems.
Purpose of the Study:
- To develop a quantum theory for optical excitations in atomic-scale materials.
- To characterize and identify single-particle-like and collective excitations.
- To investigate the nature of many-body excitations in linear atomic chains.
Main Methods:
- Utilized exact diagonalization to study many-body excitations in finite linear atomic chains (10-25 atoms).
- Employed a simplified model Hamiltonian for theoretical calculations.
- Developed criteria including transfer dipole moment, balance, transfer charge, dynamical response, and induced-charge distribution to identify plasmonic states.
Main Results:
- Exact diagonalization revealed highly correlated, multiexcitonic states dominating spectral and optical responses, unlike density functional theory (DFT) predictions.
- DFT methods failed to capture these significant excitonic many-body states.
- Identified specific criteria to distinguish plasmonic excitations from dense spectra of single-particle and excitonic states.
Conclusions:
- Excitonic states are predominant in atomic-scale materials due to local correlation possibilities.
- The developed criteria enable the identification of plasmonic states within complex excitation spectra.
- This work provides a pathway for a more accurate quantum description of optical excitations in nanoscale systems.
