Resonant Excitation Achieves Vibronic Mollow Triplets on Phonon Sidebands

Scientists have long recognised the Mollow triplet as a key spectral signature of a dressed emitter. Now, Devashish Pandey, Corne Koks, and Martijn Wubs, alongside colleagues from the Technical University of Denmark and The University of Sheffield, demonstrate that this signature extends beyond conventional expectations. Their research predicts that, for emitters coupled to localised phonons, Mollow triplets strikingly reappear on associated phonon sidebands , a phenomenon previously considered incoherent. This discovery, detailed in their new paper, reveals a direct fingerprint of dynamically generated dressed states hybridising electronic, photonic and vibrational degrees of freedom, and provides a scalable analytical formalism for modelling such effects in complex molecular systems like dibenzoterrylene , ultimately establishing a novel signature of coherence in vibronically coupled systems.

Scientists have. This formalism rigorously captures the multi-mode vibronic coupling characteristic of realistic solid-state emitters, circumventing computational bottlenecks associated with expanding Hilbert spaces. Experiments show that these vibronic Mollow triplets arise from drive-induced dressed states imprinted onto vibronic transitions, revealing a new class of vibronic dressed states and opening avenues for coherently manipulating coupled electron-phonon systems. Originally identified in atoms, the Mollow triplet has become a benchmark in quantum technologies, spanning semiconductor quantum dots, defect centers, and organic molecules.
For the Mollow triplet to appear, the Rabi frequency must exceed both spontaneous emission and decoherence rates, however, electron-phonon interactions often dominate decoherence in solid-state emitters. While the effects of bulk acoustic phonons are well understood, the impact of localized phonon interactions on Mollow physics has remained largely unexplored until now. This work provides a predictive framework for complex molecular systems, utilising a polaron transformation to incorporate strong electron-phonon correlations without increasing computational demands. The team’s master equation approach, detailed in the supporting information, accounts for the anharmonic coupling of localized phonon modes to acoustic modes, alongside spontaneous emission and pure dephasing.

Mollow Triplet Replication on Phonon Sidebands reveals strong

Scientists predicted that Mollow triplets, typically confined to the zero-phonon line, strikingly replicate on phonon sidebands when emitters are strongly driven and coupled to localized phonons. This capability offers a crucial advantage over standard numerical master equation treatments, which often introduce errors due to truncating the vibronic Hilbert space for computational tractability. The team’s method delivers an accurate and scalable framework for analysing the experimentally dominant zero-phonon line and first-order phonon sidebands in complex molecular systems, enabling detailed simulations of DBT spectra at T = 8 K, revealing ten fundamental modes and their overtones. Experiments employed normalized DBT spectra computed from a model with parameters γ = 0.094 μeV and Ω= 10γ, demonstrating the impact of laser intensity and Rabi frequency on the lifetime-limited DBT spectra for the first five fundamental local phonon modes.
The researchers obtained G(1)(τ) = e− β M X j=0 βj ” 1 4e−Cjτ + X α=±1 Λαe−S(α) j τ #, where β0 ≡1 and β = PM j=1 βj, Cj = C0+(κj/2−iνj), and S(α) j = S(α) 0 + (κj/2 −iνj). This formalism accounts for spectral weight reduction in the zero-phonon line due to local phonons, and suppressed amplitudes in phonon-assisted transitions at frequencies ω0 −νj. Furthermore, the work assessed experimental feasibility by mapping the vibronic splitting of five DBT modes to laser intensity and Rabi frequency, revealing that strongly damped modes (j = 1, 2, with κ1,2 ≈130, 160 μeV) require higher drives than lower-damping modes (j = 3, 5, with κ ≈35, 55 μeV) to achieve lifetime-limited resolution, satisfying the condition Ω≳njκj. A drive strength of Ω∼35 μeV, equivalent to a laser intensity of 20 μW/μm2, was found sufficient to observe the vibronic triplet, though the team acknowledged potential issues with photobleaching and spectral dephasing, suggesting mitigation strategies like hexagonal boron nitride or electrical gating to improve environmental stability.

Vibronic Mollow triplets reveal strong coupling in DBT

Analytical expressions derived within a dressed-atom framework exhibit excellent agreement with numerical polaron master equations, while simultaneously highlighting the distinct spectral constraints of the vibronic regime as defined by Eq. (5). Crucially, tests prove this formalism overcomes the scaling limitations of numerical methods, enabling simulations of complex systems like DBT and extending applicability to any quantum emitter coupled to high-Q localized phonon modes. Measurements confirm that the phonon sideband, traditionally viewed as an incoherent loss channel, can function as a coherent spectral resource under appropriate driving conditions. The breakthrough delivers a precise understanding of the driving conditions necessary to observe these novel spectral features, opening new avenues for quantum control across diverse solid-state platforms. This research provides a foundation for exploiting phonon sidebands as a coherent resource for quantum technologies, potentially revolutionizing quantum control strategies in solid-state systems.

Vibronic Mollow Triplets Reveal Tripartite Dressed States in

Scientists have identified the emergence of vibronic Mollow triplets, Mollow triplets appearing within the local phonon sidebands of a strongly driven quantum emitter. These spectral features indicate the formation of tripartite dressed states, arising from the coherent interaction between the emitter, the driving laser, and the vibrational environment. By extending the established dressed-atom framework, researchers derived analytical expressions that demonstrate excellent agreement with numerical polaron master equations, while also highlighting the unique spectral constraints of the vibronic regime. This formalism overcomes computational limitations associated with numerical methods, facilitating the simulation of complex systems such as dibenzoterrylene (DBT). Importantly, the findings are applicable to any quantum emitter coupled to high-quality localized phonon modes, suggesting the phonon sideband is not merely an incoherent loss channel, but potentially a coherent spectral resource for quantum control in various solid-state platforms. The authors acknowledge limitations stemming from environmental factors impacting emitter stability and drive intensity, noting that materials engineering, such as utilising hexagonal boron nitride or electrical gating, could mitigate these effects.