where ĤM describes the matter contribution due to the excitonic DOF, Ĥcav describes the cavity radiation field, and ĤLM is the light-matter interaction term. The matter Hamiltonian ĤM describes N identical and noninteracting molecules; each molecule is modeled as an effective two-level system that represents the molecule's ground state |g n ⟩ and excited state |e n ⟩ (for the n th molecule). The matter Hamiltonian is written as