论文标题
控制Cherenkov阈值
Controlling Cherenkov threshold with nonlocality
论文作者
论文摘要
通常认为，由于经典局部框架中状态极大的光子密度，Cherenkov辐射在双曲线材料中是无阈值。尽管非本地和量子效应的最新进展扩展了我们对金属纳米结构中光 - 物质相互作用的理解，但非局部性对无阈值Cherenkov辐射的影响仍然难以捉摸。从理论上讲，我们在这里证明了非局部性提供了一种必不可少的方法，可以灵活地在金属级别分层结构中设计Cherenkov阈值。特别是，非局部性导致较低的速度截止，其值与电子费米速度相当。令人惊讶的是，如果超材料围绕Epsilon-Near-Zero频率工作，那么较低的阈值可能会明显小于经典预测的阈值。控制Cherenkov阈值的能力为Cherenkov辐射的实际应用打开了许多前景，尤其是集成的自由电子辐射源。
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. While recent advances in nonlocal and quantum effects extend our understanding of light-matter interactions in metallic nanostructures, the influence of nonlocality on threshold-free Cherenkov radiation still remains elusive. Here we theoretically demonstrate that the nonlocality provides an indispensable way to flexibly engineer Cherenkov thresholds in metallodielectric layered structures. Particularly, the nonlocality results in a lower-bound velocity cutoff, whose value is comparable to the electron Fermi velocity. Surprisingly, this lower-bound threshold can be significantly smaller than the classically predicted one if the metamaterial works around epsilon-near-zero frequencies. The capability to control Cherenkov thresholds opens numerous prospects for practical applications of Cherenkov radiation, in particular, for integrated free-electron radiation sources.
