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arXiv 2001.01750physics.opticscond-mat.mes-hall
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多分子表面增强拉曼散射中的光机械集体效应

Optomechanical Collective Effects in Surface-Enhanced Raman Scattering from Many Molecules

Yuan Zhang, Javier Aizpurua, Ruben Esteban

摘要:

在表面增强拉曼散射(SERS)中,分子间的相互作用通常被忽略。在这种假设下,总的SERS信号被描述为独立处理的每个分子的单独贡献的总和。我们在这里采用腔量子电动力学框架内的SERS的光机描述来研究不同分子的量子关联如何产生集体效应。我们推导出相同分子的解析表达式,并进行数值模拟来分析两种类型的集体现象:(i)随着分子数量的增加,在强烈的照明下,激光强度阈值降低,观察到强非线性,以及(ii)在SERS信号中识别超辐射,即分子数量的二次缩放。在反斯托克斯散射中观察后者所需的激光强度相对适中,这使得它特别容易进行实验。我们的研究结果还表明,集体现象可以生存在适度的均匀和不均匀的加宽。

英文摘要:

The interaction between molecules is commonly ignored in surface-enhanced Raman scattering (SERS). Under this assumption, the total SERS signal is described as the sum of the individual contributions of each molecule treated independently. We adopt here an optomechanical description of SERS within a cavity quantum electrodynamics framework to study how collective effects emerge from the quantum correlations of distinct molecules. We derive analytical expressions for identical molecules and implement numerical simulations to analyze two types of collective phenomena: (i) a decrease of the laser intensity threshold to observe strong non-linearities as the number of molecules increases, within intense illumination, and (ii) identification of superradiance in the SERS signal, namely a quadratic scaling with the number of molecules. The laser intensity required to observe the latter in the anti-Stokes scattering is relatively moderate, which makes it particularly accessible to experiments. Our results also show that collective phenomena can survive in the presence of moderate homogeneous and inhomogeneous broadening.

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