Simple Exchange-Correlation Energy Functionals for Strongly Coupled Light-Matter Systems Based on the...

Area of Science:

• Quantum Optics
• Computational Chemistry
• Condensed Matter Physics

Background:

• Recent advances in strongly coupled light-matter systems necessitate ab initio methods.
• Quantum-electrodynamical density-functional theory (QEDFT) offers efficient calculations but lacks density-functional approximations.

Purpose of the Study:

• Introduce the first gradient-based density functional for QEDFT.
• Enable accurate and efficient first-principles calculations for large light-matter systems.

Main Methods:

• Derived a gradient-based density functional for QEDFT exchange-correlation energy using the adiabatic-connection fluctuation-dissipation theorem.
• Benchmarked the approximation on small systems in optical cavities and large fullerene molecules.

Main Results:

• Developed the first density-functional approximation for QEDFT.
• Demonstrated computationally efficient calculations for large systems (fullerenes up to C180 with 400,000 photon modes).

Conclusions:

• The new density functional approximation makes first-principles calculations of large-scale light-matter systems feasible within QEDFT.
• This work bridges quantum optics and large-scale electronic structure theory.