Collective resonance displacement in strongly driven cold atoms

Cold atoms are promising platforms for metrology and quantum computation, yet their many-body dynamics remains largely unexplored. We here investigate Rabi oscillations from optically-thick cold clouds, driven by high-intensity coherent light. A dynamical displacement from the atomic resonance is predicted, which can be detected through the collective Rabi oscillations of the atomic ensemble. Different from linear-optics shifts, this dynamical displacement grows quadratically with the optical depth, yet it reduces with increasing pump power as dipole-dipole interactions are less effective.