Interfacial Cherenkov radiation from ultralow-energy electrons

作者：Zheng Gong, Jialin Chen, Ruoxi Chen, Xingjian Zhu, Chan Wang, Xinyan Zhang, Hao Hu, Yi Yang, Baile Zhang, Hongsheng Chen, Ido Kaminer, Xiao Lin · 发表于：Proceedings of the National Academy of Sciences · 年份：2023 · DOI：10.1073/pnas.2306601120 · 被引用次数：24 · 研究领域：Terahertz technology and applications、Strong Light-Matter Interactions、Metamaterials and Metasurfaces Applications

Cherenkov radiation occurs only when a charged particle moves with a velocity exceeding the phase velocity of light in that matter. This radiation mechanism creates directional light emission at a wide range of frequencies and could facilitate the development of on-chip light sources except for the hard-to-satisfy requirement for high-energy particles. Creating Cherenkov radiation from low-energy electrons that has no momentum mismatch with light in free space is still a long-standing challenge. Here, we report a mechanism to overcome this challenge by exploiting a combined effect of interfacial Cherenkov radiation and umklapp scattering, namely the constructive interference of light emission from sequential particle-interface interactions with specially designed (umklapp) momentum-shifts. We find that this combined effect is able to create the interfacial Cherenkov radiation from ultralow-energy electrons, with kinetic energies down to the electron-volt scale. Due to the umklapp scattering for the excited high-momentum Bloch modes, the resulting interfacial Cherenkov radiation is uniquely featured with spatially separated apexes for its wave cone and group cone.