Nonlinear valley phonon scattering under the strong coupling regime

Liu, Xiaoze; Yi, Jun; Yang, Sui; Lin, Erh Chen; Zhang, Yue Jiao; Zhang, Peiyao; Li, Jian Feng; Wang, Yuan; Lee, Yi Hsien; Tian, Zhong; Zhang, Xiang

doi:10.1038/s41563-021-00972-x

Cited by 38 publications

(34 citation statements)

References 31 publications

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“…Future possibilities to identify unambiguous optomechanical molecular dynamics might examine the correlations of emitted photons or, alternatively, access specific optomechanical signatures such as optomechanically induced transparency 24 or a strong dependence on laser detuning. 1 , 22 , 32 Coupling the plasmon with phonons in solids or van der Waals materials 31 , 56 opens an alternative path to exploiting optomechanical interactions at the nanoscale.…”

Section: Discussionmentioning

confidence: 99%

Molecular Optomechanics Approach to Surface-Enhanced Raman Scattering

2022

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Conspectus Molecular vibrations constitute one of the smallest mechanical oscillators available for micro-/nanoengineering. The energy and strength of molecular oscillations depend delicately on the attached specific functional groups as well as on the chemical and physical environments. By exploiting the inelastic interaction of molecules with optical photons, Raman scattering can access the information contained in molecular vibrations. However, the low efficiency of the Raman process typically allows only for characterizing large numbers of molecules. To circumvent this limitation, plasmonic resonances supported by metallic nanostructures and nanocavities can be used because they localize and enhance light at optical frequencies, enabling surface-enhanced Raman scattering (SERS), where the Raman signal is increased by many orders of magnitude. This enhancement enables few- or even single-molecule characterization. The coupling between a single molecular vibration and a plasmonic mode constitutes an example of an optomechanical interaction, analogous to that existing between cavity photons and mechanical vibrations. Optomechanical systems have been intensely studied because of their fundamental interest as well as their application in practical implementations of quantum technology and sensing. In this context, SERS brings cavity optomechanics down to the molecular scale and gives access to larger vibrational frequencies associated with molecular motion, offering new possibilities for novel optomechanical nanodevices. The molecular optomechanics description of SERS is recent, and its implications have only started to be explored. In this Account, we describe the current understanding and progress of this new description of SERS, focusing on our own contributions to the field. We first show that the quantum description of molecular optomechanics is fully consistent with standard classical and semiclassical models often used to describe SERS. Furthermore, we note that the molecular optomechanics framework naturally accounts for a rich variety of nonlinear effects in the SERS signal with increasing laser intensity. Furthermore, the molecular optomechanics framework provides a tool particularly suited to addressing novel effects of fundamental and practical interest in SERS, such as the emergence of collective phenomena involving many molecules or the modification of the effective losses and energy of the molecular vibrations due to the plasmon–vibration interaction. As compared to standard optomechanics, the plasmonic resonance often differs from a single Lorentzian mode and thus requires a more detailed description of its optical response. This quantum description of SERS also allows us to address the statistics of the Raman photons emitted, enabling the interpretation of two-color correlations of the emerging photons, with potential use in the generation of nonclassical states of light. Current SERS experimental implementations in organic molecules and two-dimensional la...

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Section: Discussionmentioning

confidence: 99%

Molecular Optomechanics Approach to Surface-Enhanced Raman Scattering

2022

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“…In the experiment, this phenomenon should be shown as (1) the nonlinear enhancement of the SERS signal and (2) anomalous anti-Stokes/Stokes intensity ratio, which is strongly dependent on the laser-plasmon detuning and the optomechanical coupling rate . To verify that, previous studies were mainly based on single-wavelength power dependence in the system of nanocavity-coupled small number individual molecules, , or phonons mediated by exciton resonance . However, a comprehensive self-consistent demonstration linking nonlinear power dependence and laser-plasmon detuning is still lacking.…”

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confidence: 99%

Phononic Cavity Optomechanics of Atomically Thin Crystal in Plasmonic Nanocavity

Chen

et al. 2022

ACS Nano

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In the picture of molecular cavity optomechanics, surface-enhanced Raman scattering (SERS) can be understood as molecular oscillators parametrically coupled to plasmonic nanocavities supporting an extremely localized optical field. This enables SERS from conventional fingerprint detection toward quantum nanotechnologies associated with, e.g., frequency upconversion and optomechanically induced transparency. Here, we study a phononic cavity optomechanical system consisting of a monolayer MoS 2 placed inside a plasmonic nanogap, where the coherent phonon−plasmon interaction involves the collective oscillation from tens of thousands of unit cells of the MoS 2 crystal. We observe the selective nonlinear SERS enhancement of the system as determined by the laser-plasmon detuning, suggesting the dynamic backaction modification of the phonon populations. Anomalous superlinear power dependence of a second-order Ramaninactive phonon mode with respect to the first-order phonons is also observed, indicating the distinctive properties of the phononic nanodevice compared with the molecular system. Our results promote the development of robust phononic optomechanical nanocavities to further explore the related quantum correlation and nonlinear effects including parametric instabilities.

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“…A strong dependence on cavity detuning as well as a clear retention of valley polarization of both exciton polaritons and trion-polaritons was observed. In a follow-up work from the same group, the rotation of the valley pseudospin vector was achieved by using an external magnetic field [354] .Other important valley related phenomena have been observed at cryogenic temperatures by Lundt et al and Liu et al that demonstrated the optical valley Hall effect in a monolayer MoSe 2 microcavity [351] and the stimulated valley phonon scattering in a MoS 2 plasmonic cavity, respectively [351,355] .…”

Section: Valley Polarization In Tmd Microcavitiesmentioning

confidence: 94%

Microcavity exciton polaritons at room temperature

Ghosh

Zhao

et al. 2022

Photonics Insights

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The quest for realizing novel fundamental physical effects and practical applications in ambient conditions has led to tremendous interest in microcavity exciton polaritons working in the strong coupling regime at room temperature. In the past few decades, a wide range of novel semiconductor systems supporting robust exciton polaritons have emerged, which has led to the realization of various fascinating phenomena and practical applications. This paper aims to review recent theoretical and experimental developments of exciton polaritons operating at room temperature, and includes a comprehensive theoretical background, descriptions of intriguing phenomena observed in various physical systems, as well as accounts of optoelectronic applications. Specifically, an in-depth review of physical systems achieving room temperature exciton polaritons will be presented, including the early development of ZnO and GaN microcavities and other emerging systems such as organics, halide perovskite semiconductors, carbon nanotubes, and transition metal dichalcogenides. Finally, a perspective of outlooking future developments will be elaborated.

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Nonlinear valley phonon scattering under the strong coupling regime

Cited by 38 publications

References 31 publications

Molecular Optomechanics Approach to Surface-Enhanced Raman Scattering

Molecular Optomechanics Approach to Surface-Enhanced Raman Scattering

Phononic Cavity Optomechanics of Atomically Thin Crystal in Plasmonic Nanocavity

Microcavity exciton polaritons at room temperature

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