Interfacial Cherenkov radiation from ultralow-energy electrons

• Main Authors: Gong, Zheng, Chen, Jialin, Chen, Ruoxi, Zhu, Xingjian, Wang, Chan, Zhang, Xinyan, Hu, Hao, Yang, Yi, Zhang, Baile, Chen, Hongsheng, Kaminer, Ido, Lin, Xiao
• Other Authors: School of Physical and Mathematical Sciences
• Format: Article
• Language: English
• Published: 2024
• Subjects: Physics; Cherenkov Radiation; Transition Radiation
• Online Access: https://hdl.handle.net/10356/173491
• Institution: Nanyang Technological University

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.