Triple-quantum dual-comb two-dimensional coherent spectroscopy resolves velocity-synchronized Dicke states in hot atomic vapors

Two-dimensional coherent spectroscopy (2DCS) combined with dual-comb technology offers unprecedented resolution for probing many-body interactions and correlations in atomic vapors, yet its application to high-order multi-quantum transitions remains challenging due to weaker nonlinear signals and phase instability. Here, we demonstrate a triple-quantum dual-comb 2DCS technique that achieves λ/110 phase stability through digital correction, enabling the observation of velocity-synchronized Dicke states in a thermal rubidium vapor. By resolving collective hyperfine resonances of ⁸⁵Rb and ⁸⁷Rb isotopes with 100 MHz spectral resolution, we reveal that triple-quantum dipole-dipole correlations (0.95) surpass double-quantum counterparts (0.90), indicating tighter velocity matching in higher-order Dicke states. This work establishes a pathway for manipulating multi-atom correlations in Doppler-broadened systems and extends 2DCS to research the many-body interaction in semiconductor exciton and 2D materials.