Strong Light–Matter Coupling and Field Quantization in a Dinickel Molecular Resonator

Field quantization is fundamental to quantum optics and polaritonic chemistry, enabling exploration of light–matter interactions at the quantum level. We report resonant coupling between the two-level excitation of a dinickel (Ni₂) complex and its locally recycled scattering field under ambient, cavity-free conditions. This Ni₂ system exhibits hallmark resonance-fluorescence features, including Rabi doublets and Mollow triplets, with strong coupling achieved under weak, non-resonant excitation. The Ni₂ unit functions as a diatomic resonator, enhancing photon scattering and forming a Jaynes–Cummings molecule. Simulations of second-order correlation functions confirm photon antibunching and underdamped Rabi oscillations. Collective coupling strength scales linearly with the number of molecules (N), surpassing Tavis–Cummings model predictions and reaching the ultrastrong coupling regime. These findings establish Ni₂ complexes as robust molecular quantum systems, offering a chemically tunable platform for quantum information processing and coherent chemical control at the molecular scale.