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摘要: 极化激元是光与不同极化子相互作用形成的半光半物质的准粒子,可用于亚波长尺度的光场调控,在光学成像、非线性效应增强及新型超构材料设计等领域扮演着举足重轻的角色。近年来,随着人们对转角范德华尔斯材料体系的制备工艺和物性研究的不断深入,其中许多新奇的极化激元现象也被揭示。本文综述了近年来转角范德华尔斯材料在光学领域的研究进展,包含转角石墨烯体系中的等离极化激元,转角二维过渡金属硫化物中的激子极化激元与六方氮化硼(h-BN)与 α-MoO3体系中的声子极化激元等。最后展望转角二维范德华尔斯材料中的极化激元在纳米尺度下光与物质相互作用的有效控制方面所展现的巨大潜力。Abstract: Polaritons are half-light, half-matter quasi-particles formed by the interaction of light and different polarons. They can be applied for light-control at sub-wavelength scales and have shown intriguing potential for optical imaging, enhanced nonlinear optics and novel metamaterial design. Recent advances in the twistronics of two-dimensional van der Waals materials have enabled a vast variety of extraordinary phenomena associated with moiré physics, which also inspired new direction for the research of polaritons. In this article, we briefly review the rise of “twist-photonics”, including plasmon polaritons in twisted graphene system, exciton polaritons in a twisted transition-metal dichalcogenide system and phonon polaritons in a twisted h-BN and α-MoO3 system. Twist van der Waals materials may offer new directions to manipulate light-matter interactions at nanoscale.
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Key words:
- twistronics /
- two-dimensional materials /
- van der Waals materials /
- polaritons
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图 1 (a)红外s-SNOM 测量转角双层石墨烯的示意图[15];(b)显示转角双层石墨烯中由孤子超晶格形成的光子晶体(左);转角双层石墨烯样品的TEM 暗场图像(右)[15];(c)石墨烯/h-BN 电子能带结构的三维模拟结构图[26]
Figure 1. (a) Schematic of the IR nano-imaging of twisted bilayer graphene (TBG). Reproduced with permission. Copyright 2018, Science (New York, N.Y.); (b) (Left) Visualizing the nano-light photonic crystal formed by the soliton lattice. (Right) Dark-field TEM image of a TBG sample. Reproduced with permission. Copyright 2018, Science (New York, N.Y.); (c) 3D representation of the electronic band structure of graphene/h-BN. Reproduced with permission. Copyright 2015, Nat Mater.
图 2 (a)层间激子的莫尔电位[16];(b)K谷激子的空间图[16];(c)被困在莫尔电位中的激子示意图[17];(d)单层WSe2和WS2区域上测得的偏振相关的二次谐波信号图[18];(e)MoSe2/WS2的能带示意图[19];(f)MoSe2/WS2的光致发光图像[19]
Figure 2. (a) The moiré potential of the interlayer exciton transition. Reproduced with permission. Copyright 2019, Nature; (b) Spatial map of the optical selection rules for K-valley excitons. Reproduced with permission. Copyright 2019, Nature; (c) Schematic of an exciton trapped in a moiré potential site. Reproduced with permission. Copyright 2019, Nature; (d) The polarization-dependent second harmonic generation signal measured on the monolayer WSe2 and WS2. Reproduced with permission. Copyright 2019, Nature; (e) Schematic of the MoSe2/WS2 band structure; (f) The PL image of MoSe2/WS2. Reproduced with permission. Copyright 2019, Nature.
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