Our paper on Casimir-Lifshitz Theory for Cavity Modification of Ground-State Energy has been published in Physical Review Letters today as a Christmas gift!

Understanding how cavities modify the ground state of matter is a fundamental question in quantum electrodynamics. In this work, we present a nonperturbative macroscopic QED theory that accounts for the infinite number of cavity modes with a continuum of their wave vectors, going beyond the commonly used single-mode Hopfield Hamiltonian.

Based on Lifshitz’s theory for vacuum energy and employing a Lorentz model for the material permittivity, we reveal how static screening at very low frequencies is the main driver of cavity-induced ground-state energy shifts, rather than resonant polaritons. The theory naturally incorporates losses and temperature effects, providing a comprehensive framework for understanding cavity modifications of matter.

This work, by Oleg Kotov, is based on a collaboration we started when he was a postdoc with Timur Shegai (Chalmers University of Technology) before moving to Madrid.