Cherenkov radiation is generally believed to be threshold‐free in hyperbolic metamaterials owing to the extremely large photonic density of states in classical local framework. Although recent advances in nonlocal and quantum plasmonics extend our understanding of light‐matter interactions in metamaterials, how such effects influence Cherenkov radiation in hyperbolic metamaterials still remains unknown. Here, it is demonstrated that effects of nonlocality add a new degree of freedom to engineer Cherenkov thresholds in hyperbolic metamaterials. The interplay between finite structural dimensions and nonlocal nature of metallic electrons results in a nonzero Cherenkov threshold. Counterintuitively, such nonlocality‐induced Cherenkov threshold can be significantly smaller than the classically predicted one if the metamaterial is designed to work around the epsilon‐near‐zero frequency. This phenomenon is attributed to the excitation of longitudinal plasmon modes which are absent in classical electromagnetic framework. These findings apply to a general class of hyperbolic materials, including metallodielectric layered structures, nanorod/nanoribbon arrays, hyperbolic van der Waals crystals, etc.

中文翻译：

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非局部性引起的Cherenkov阈值

通常认为，由于经典局部框架中状态的光子密度非常大，因此在双曲超材料中，切伦科夫辐射是无阈值的。尽管非局部和量子等离激元的最新进展扩展了我们对超材料中光-质相互作用的理解，但这种影响如何影响双曲超材料中的切伦科夫辐射仍然未知。在这里，证明了非局部性的影响为双曲线超材料中的切伦科夫阈值的工程设计增加了新的自由度。有限的结构尺寸和金属电子的非局部性质之间的相互作用导致非零的契伦科夫阈值。违反直觉，如果超材料被设计为在ε接近零的频率附近工作，那么这种由非局部性引起的Cherenkov阈值可以大大小于经典预测的阈值。这种现象归因于经典电磁框架中不存在的纵向等离子体激元模式的激发。这些发现适用于一般双曲线材料，包括金属电介质层状结构，纳米棒/纳米带阵列，双曲线范德华晶体等。