Quantum-electrodynamical time-dependent density functional theory within Gaussian atomic basis

Area of Science:

• Quantum chemistry
• Theoretical chemistry
• Computational physics

Background:

• Quantum-electrodynamical time-dependent density functional theory (QED-TDDFT) describes electron-photon interactions.
• Previous formulations may pose challenges for analytic derivative development.

Purpose of the Study:

• To implement QED-TDDFT using dimensionless amplitudes for Hermitian coupling matrices.
• To investigate the impact of approximations and excited states on polaritons in optical cavities.

Main Methods:

• Developed a Gaussian atomic basis implementation of QED-TDDFT.
• Employed dimensionless amplitudes for photonic contributions.
• Examined effects of dipole self-energy, rotating-wave approximation, and Tamm-Dancoff approximation.

Main Results:

• Achieved a Hermitian QED-TDDFT coupling matrix, aiding future analytic derivative development.
• Highlighted the significant role of higher-energy, off-resonance states in strong coupling regimes.
• Demonstrated that these states influence polariton energies and compositions.

Conclusions:

• The proposed QED-TDDFT implementation accurately accounts for crucial excited states in optical cavities.
• This method provides a robust framework for studying light-matter interactions and polariton formation.
• Facilitates advancements in theoretical descriptions of quantum electrodynamics in molecular systems.