Abstract
Abstract The combination of 2D materials and surface plasmon can produce some novel optical phenomena that have attracted much attention. Illuminated by light with different polarization states, the field distribution around the plasmonic structure can control the light-matter interaction. The interaction between graphene and light can be strongly enhanced by employing radially polarized beams in a nanocavity. Here, we study the selectively enhanced vibration of graphene in a coupled plasmonic gold nanocavity with a radially polarized optical field, and the coupling and enhancing mechanisms are investigated both experimentally and numerically. By focusing a radially polarized beam, a high z component of a localized near field in the nanocavity is provided to strongly enhance the interaction between graphene and light, which can be used to enhance the vibrational signal of the interlayer. For the in-plane vibration of graphene, a similar enhancement is obtained with a linearly and radially polarized optical field. A plasmonic nanocavity is used to enhance the vibration of graphene, which provides potential applications in studying the out-of-plane vibration mode and exploring the mechanism of the interlayer coupling of 2D materials.
Highlights
With the family developed from graphene, two-dimensional (2D) materials such as transition metal dichalcogenides, hexagonal boron nitride [1,2,3], and many novel 2D materials [4,5,6,7] have attracted much attention due to their extraordinary properties, which include high carrier mobility, wide range optical absorption, and atomic thickness
Nobel metal nanostructures can confine the light to the surface of metal, which provides a strong enhancement of the electromagnetic (EM) field, thereby strengthening the weak absorption of 2D materials as well as the light-matter interaction [21,22,23,24,25]
Hydrochloric acid (HCl), ammonium persulfate, polyvinyl pyrrolidone (PVP), polymethyl methacrylate (PMMA) and acetone solution were purchased from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China)
Summary
With the family developed from graphene, two-dimensional (2D) materials such as transition metal dichalcogenides, hexagonal boron nitride [1,2,3], and many novel 2D materials [4,5,6,7] have attracted much attention due to their extraordinary properties, which include high carrier mobility, wide range optical absorption, and atomic thickness. The nanogap distance of such 2D materials-plasmon nanocavity hybrid structure can be tuned by changing the interlayer number of 2D materials from subnanometer to several nanometers, which has been used to study the quantum effect and enhance the light-matter interaction [36,37,38]. The coupling effects are studied by employing Raman signal through a hybrid system composed of an Au nanorod and Au microplate spaced by graphene under a radially- and linearly-polarized-beam excitation. Comparing the hybrid system excited by a linearly and radially polarized beam, the results show that the difference between the enhancement effect under different polarization states is small due to the mismatch of the Raman vibration mode and the plasmon mode. It may provide potential application in exploring the superconductivity mechanism of twisted 2D materials
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