Electron-Phonon Entanglement Effects in Polarons Localization

Numerous experimental observations indicate the presence of localized polarons. This localization is also reflected in DFT-based calculations, shown by the polaron formation energy, electronic wavefunctions, and nuclear displacements. In these calculations, the polaron states are not eigenstates of the full Hamiltonian but are modeled using an adiabatic approximation, which overlooks potential entanglement of electronic and vibronic degrees of freedom. Conversely, the exact many-body eigenstates of the full electron–phonon Hamiltonian are inherently delocalized Bloch functions. This discrepancy raises the question of whether electron self-localization, as seen in current methods, is a real physical effect or an artifact of approximate modeling. We investigate the effect of electron–phonon entanglement within the Holstein polaron model, in a work laying the foundation for a first-principles approach to entanglement-driven polaron physics.