Nonlocality induced Cherenkov threshold

• Main Authors: Hu, Hao, Lin, Xiao, Zhang, Jingjing, Liu, Dongjue, Genevet, Patrice, Zhang, Baile, Luo, Yu
• Other Authors: School of Electrical and Electronic Engineering
• Format: Article
• Language: English
• Published: 2022
• Subjects: Engineering::Electrical and electronic engineering::Optics, optoelectronics, photonics; Cherenkov Radiation; Hyperbolic Metamaterials
• Online Access: https://hdl.handle.net/10356/154599
• Institution: Nanyang Technological University

Cherenkov radiation is generally believed to be threshold-free in hyperbolicmetamaterials owing to the extremely large photonic density of states in classical localframework. Although recent advances in nonlocal and quantum plasmonics extend ourunderstanding of light-matter interactions in metamaterials, how such effects influenceCherenkov radiation in hyperbolic metamaterials still remains unknown. Here, it isdemonstrated that effects of nonlocality add a new degree of freedom to engineerCherenkov thresholds in hyperbolic metamaterials. The interplay between finite structuraldimensions and nonlocal nature of metallic electrons results in a nonzero Cherenkovthreshold. Counterintuitively, such nonlocality-induced Cherenkov threshold can besignificantly smaller than the classically predicted one if the metamaterial is designed to workaround the epsilon-near-zero frequency. This phenomenon is attributed to the excitation oflongitudinal plasmon modes which are absent in classical electromagnetic framework. Thesefindings apply to a general class of hyperbolic materials, including metallodielectric layeredstructures, nanorod/nanoribbon arrays, hyperbolic van der Waals crystals, etc.