Two-dimensional coherent spectroscopy (2DCS) combined with dual-comb technology offers unprecedented resolutionfor probing many-body interactions in atomic vapors, yet its application to high-order multi-quantumtransitions remainschallenging due to weaker nonlinear signals and phase instability. Here, we demonstrate a triple-quantumdual-comb2DCS 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 and87Rbisotopes with 100 MHz spectral resolution, the titled and elongated ellipticity of the three-quantum peak line shape (0.94)is higher than that of the double-quantum (0.84), reveals that triple-quantum (TQS) correlations (0.95) surpass double-quantum counterparts (0.90), indicating tighter velocity matching in higher-order Dicke states. This work provides a pathway for manipulating multi-atom correlations in Doppler-broadened systems, and greatly assists to characterize complex hyperfine many-body interaction in semiconductor exciton and two-dimensional materials.
Abstract 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.
Frequency-comb based multidimensional coherent spectroscopy is a novel optical method that enables high-resolution measurement in a short acquisition time. The method's resolution makes multidimensional coherent spectroscopy relevant for atomic systems that have narrow resonances. We use double-quantum multidimensional coherent spectroscopy to reveal collective hyperfine resonances in rubidium vapor at 100 °C induced by dipole-dipole interactions. We observe tilted and elongated line shapes in the double-quantum 2D spectra, which have never been reported for Doppler-broadened systems. The elongated line shapes suggest that the signal is predominately from the interacting atoms that have a near zero relative velocity.
We report dual-comb spectroscopy of the collective zero-quantum response of rubidium atoms. The observed signals include two-atom collective resonances at 2( ω D 2 − ω D 1 ), ω 5 P 3/2 →5 D − ω D 2 , ω 5 P 3/2 →5 D − ω D 1 , and ( ω D 2 − ω D 1 )+( ω 5 P 3/2 →5 D − ω D 1 ), as well as higher-order three-atom resonances. Unlike double-quantum spectroscopy, which probes sum-frequency resonances of multiple atoms, the zero-quantum pathway probes difference-frequency correlations between optical transitions. In a dual-comb implementation, these signals are independent of the carrier-envelope offset frequencies of both combs, enabling rapid measurements without active carrier-envelope offset stabilization. These results show that zero-quantum dual-comb spectroscopy is a powerful approach for probing collective coherences and many-body correlations in atomic systems.
Many-body interactions and correlations in atomic ensembles are fundamental in understanding many-body effects such as collective and emergent phenomena and also play an important role in various atom-based applications. Optical two-dimensional coherent spectroscopy (2DCS) provides a powerful tool to measure many-body interactions and correlations. Here, we present the study of many-body dipole-dipole interactions and correlations in potassium and rubidium atomic vapors by using double-quantum and multi-quantum 2DCS. The results show that double-quantum 2DCS provides sensitive and background-free detection of weak dipole-dipole interaction between atoms with a mean separation up to about 16 μm, and multi-quantum 2DCS can excite and detect multi-atom states (Dicke states) with up to eight correlated atoms. The technique of optical 2DCS can provide a new approach to study many-body physics in atomic ensembles and can be potentially implemented to measure many-body effects in cold atoms and other atomic/molecular systems.
We report a novel, to the best of our knowledge, double-quantum-zero-quantum two-dimensional coherent spectroscopy (2DCS) that allows direct detection of the quantum coherence between multiparticle collective states. Through correlating the double-quantum coherence and the zero-quantum coherence, signatures for coherence between collective states can be well isolated as side peaks and readily identified in the 2D spectrum. The experiment is implemented in a vapor of rubidium atoms in a collinear 2DCS setup. Good agreement with a theoretical simulation using density matrix confirms the essential role of the interatomic correlation effect in generating the side peak signals. This 2D spectrum technique paves a new avenue for studying the coherent coupling of highly excited states and many-body properties.
Optical two-dimensional coherent spectroscopy (2DCS) has become a powerful tool for studying energy-level structure, dynamics, and coupling in many systems including atomic ensembles. Various types of two-dimensional (2D) spectra, including the so-called single-quantum, zero-quantum, and double-quantum 2D spectra, of both
D lines (
D1 and
D2 transitions) of potassium (K) atoms have been reported previously. For rubidium (Rb), a major difference is that the
D lines are about 15 nm apart as opposed to only about 3 nm for K. Simultaneously exciting both
D lines of Rb atoms requires a broader laser bandwidth for the experiment. Here, we report a broadband optical 2DCS experiment in a Rb atomic vapor. A complete set of single-quantum, zero-quantum, and double-quantum 2D spectra including both
D lines of Rb atoms were obtained. The experimental spectra were reproduced by simulated 2D spectra based on the perturbation solutions to the optical Bloch equations. This work in Rb atoms complements previous 2DCS studies of K and Rb with a narrower bandwidth that covers two
D lines of K or only a single
D line of Rb. The broadband excitation enables the capability to perform double-quantum and multiquantum 2DCS of both
D lines of Rb to study many-body interactions and correlations in comparison with K atoms.