Confining optical fields to molecular dimensions is a central objective in nanophotonics and molecular quantum optics. Here, we report strong coupling of the Mo Mo stretching vibration to a locally confined Raman scattering field in quadruply bonded dimolybdenum complexes. Under ambient, cavity-free conditions, the dimolybdenum formamidinate complexes Mo2(DAniF)4 and Mo2(DTolF)4 exhibit Rabi-type splitting, Mollow-type sidebands, and higher-order Raman features centered near the Mo Mo stretching frequency of 400 cm-1, indicating formation of dressed vibration field states. The sideband displacements from the resonance follow the photon-number-dependent relation Ωn=Ωνn, consistent with Jaynes Cummings-type coupling, while strongly displaced Raman features are assigned to leapfrog transitions within the same dressed-state ladder. In contrast, the less polarizable Mo2(O2CCH3)4 complex exhibits essentially a single Mo Mo stretching band. Reanalysis of reported resonance Raman spectra of an alkynyl Mo2 complex further supports this coupling framework. These results suggest that the Mo2 unit simultaneously serves as the Raman active oscillator and the molecular resonator that supports, confines, and enhances the locally generated scattering field, providing spectroscopic evidence for vibration field coupling and optical-field confinement within a chemically defined metal metal bond.
Confining optical fields to molecular dimensions is a central objective in nanophotonics and molecular quantum optics. Here, we report strong coupling of the Mo Mo stretching vibration to a locally confined Raman scattering field in quadruply bonded dimolybdenum complexes. Under ambient, cavity-free conditions, the dimolybdenum formamidinate complexes Mo2(DAniF)4 and Mo2(DTolF)4 exhibit Rabi-type splitting, Mollow-type sidebands, and higher-order Raman features centered near the Mo Mo stretching frequency of 400 cm-1, indicating formation of dressed vibration field states. The sideband displacements from the resonance follow the photon-number-dependent relation Ωn=Ωνn, consistent with Jaynes Cummings-type coupling, while strongly displaced Raman features are assigned to leapfrog transitions within the same dressed-state ladder. In contrast, the less polarizable Mo2(O2CCH3)4 complex exhibits essentially a single Mo Mo stretching band. Reanalysis of reported resonance Raman spectra of an alkynyl Mo2 complex further supports this coupling framework. These results suggest that the Mo2 unit simultaneously serves as the Raman active oscillator and the molecular resonator that supports, confines, and enhances the locally generated scattering field, providing spectroscopic evidence for vibration field coupling and optical-field confinement within a chemically defined metal metal bond.
Quadruply Bonded Mo2 Molecules Acting as an Inborn Emitter-Resonator Quantum System in Free Space
In recent decades, significant progress has been made in construction and study of individual quantum systems consisting of the basic single matter and energy particles, i.e., atoms and photons, which show great potentials in quantum computation and communication. Here, we demonstrate that the quadruply-bonded Mo2 unit of the complex can trap photons of visible light under ambient conditions, producing intense local electromagnetic (EM) field that features squeezed states, photon antibunching, and vacuum Rabi splitting. Our results show that both the electronic and vibrational states of the Mo2 molecule are modified by coherent coupling with the scattered photons of the Mo2 unit, as evidenced by the Rabi doublet4 and the Mollow triplet in the incoherent resonance fluorescence and the Raman spectra. The Mo2 molecule, acting as an independent emitter-resonator integrated quantum system, allows optical experiments to be conducted in free space, enabling fundamental quantum phenomena to be observed through conventional spectroscopic instrumentation. This provides a new platform for study of field effects and quantum electrodynamics (QED) in the optical domain. The insights gained from this study advance our understanding in metal-metal bond chemistry, molecular physics and quantum optics, with applications in quantum information processing, optoelectronic devices and control of chemical reactivity.
In recent decades, significant progress has been made in constructing and studying individual quantum systems based on two level atoms (molecules) and photons. Here we demonstrate that the quadruply bonded Mo2 unit, with a MoMo bond distance as short as 2.1A, functions as an innate emitter resonator molecular quantum system capable of trapping visible light photons between the two molybdenum atoms under ambient conditions, thereby generating an intense quantized local electromagnetic field with an extremely small mode volume. The resonance fluorescence spectra of three Mo2 complexes indicate that the intermetallic Mo-Mo charge transfer transition is coherently coupled to the local scattering field, exhibiting vacuum Rabi splitting and Mollow triplets. Resonant coupling of single molecules and N-molecule ensembles to the scattered light through sideband excitation produces a sequence of discrete optical modes spanning a broad wavelength range, with polaritonic transitions identical to those observed in Ni2 based systems. These results establish the Mo2 molecule as an independent emitter resonator integrated quantum system that enables quantum optical experiments in free space using conventional spectroscopic instrumentation. This work extends quantum electrodynamics into molecular science, providing new insights into metal metal bonding, molecular physics, and light matter interactions.
ABSTRACT In recent decades, significant progress has been made in constructing and studying individual quantum systems based on two‐level atoms (molecules) and photons. Here we demonstrate that the quadruply bonded Mo 2 unit, with a Mo─Mo bond distance as short as 2.1 Å, functions as an innate emitter–resonator molecular quantum system capable of trapping visible‐light photons between the two molybdenum atoms under ambient conditions, thereby generating an intense quantized local electromagnetic field with an extremely small mode volume. The resonance fluorescence spectra of three Mo 2 complexes indicate that the intermetallic Mo→Mo charge‐transfer transition is coherently coupled to the local scattering field, exhibiting vacuum Rabi splitting and Mollow triplets. Resonant coupling of single molecules and N ‐molecule ensembles to the scattered light through sideband excitation produces a sequence of discrete optical modes spanning a broad wavelength range, with polaritonic transitions identical to those observed in Ni 2 ‐based systems. These results establish the Mo 2 molecule as an independent emitter–resonator integrated quantum system that enables quantum‐optical experiments in free space using conventional spectroscopic instrumentation. This work extends quantum electrodynamics into molecular science, providing new insights into metal–metal bonding, molecular physics, and light–matter interactions.
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.
The Mollow triplet is the definitive spectral signature of an optically dressed quantum emitter. We predict that for emitters coupled to localized phonons, this signature is not confined to the zero-phonon line. Under a strong resonant drive, we show that Mollow triplets are strikingly replicated on the associated phonon sidebands -a surprising result, given that phonon sidebands are typically viewed as incoherent, inelastic scattering pathways. These vibronic Mollow triplets are a direct fingerprint of dynamically generated dressed states that hybridize the emitter's electronic, photonic, and vibrational degrees of freedom. We develop a scalable analytical formalism to model this effect in complex, multi-mode molecular systems, such as dibenzoterrylene. Our work provides the precise driving conditions for observing these novel spectral features, establishing a new signature of coherence in vibronically coupled systems.
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.