Breakdown of the Born–Oppenheimer Approximation in Strongly Correlated Polaron Systems: Implications for Non-Adiabatic Charge Transport in Two-Dimensional Perovskite Heterostructures

Abstract

The Born–Oppenheimer approximation (BOA) has long served as a foundational pillar in condensed matter and molecular physics, yet its validity in strongly correlated polaron systems remains insufficiently scrutinized. This study systematically examines the breakdown regimes of the BOA within two-dimensional hybrid organic–inorganic perovskite heterostructures by employing a combination of many-body perturbation theory, non-adiabatic path-integral molecular dynamics, and time-resolved angle-resolved photoemission spectroscopy (tr-ARPES). We identify critical electron–phonon coupling thresholds beyond which adiabatic decoupling fails catastrophically, producing anomalous charge transport signatures including negative differential mobility and sub-Drude optical conductivity. Our findings challenge prevailing models of polaron hopping and provide a revised non-adiabatic Hamiltonian framework that quantitatively reproduces experimental observations, with significant implications for next-generation perovskite-based optoelectronic device engineering.