Variational Polaron Theory for Ground States of Strongly Coupled Light-Matter and Electron-Phonon Systems
The method addresses strongly coupled light-matter and electron-phonon systems where standard approximations fail. It uses a state-dependent polaron transformation to create a transformed Hamiltonian that becomes decoupled in the strong coupling limit. By optimizing coefficients and adding a second-order correction, this nonperturbative approach provides an accurate, compact basis for molecular polariton and polaron ground states across all coupling regimes.