近日，武汉大学的肖孟&万端端及其研究团队取得一项新进展。经过不懈努力，他们证实有限势垒束缚态的存在。相关研究成果已于2024年3月8日在国际知名学术期刊《光：科学与应用》上发表。

该研究团队证实，在特定波矢下，部分边界模式的隧穿概率显著降低，几乎消失。因此，这些边界模式能够像连续介质中的束缚态一样，被完全俘获在极少的晶格格位内，导致体带隙的界限变得模糊不清。更有趣的是，被俘获的态的数量与沿边界法向分布的晶格格位数量相吻合。

研究人员通过两种不同构型的设计，并在微波频率的介电光子晶体中进行了实验验证，证实了这种特殊的有限势垒态的存在。这项研究不仅为调控局域态与通道间的耦合提供了极大的灵活性，而且开创了一种前所未有的光操纵新机制。

据悉，局限于晶格某一侧边界的模式可能会隧穿到另一侧，进而引发不必要的耦合。传统观念认为，随着系统尺寸的增大，这种隧穿的概率会呈指数级降低，因此，在变得足够小、可以忽略不计之前，需要足够多的晶格位。

附：英文原文

Title: Finite barrier bound state

Author: Liu, Tao, Bai, Kai, Zhang, Yicheng, Wan, Duanduan, Lai, Yun, Chan, C. T., Xiao, Meng

Issue&Volume: 2024-03-08

Abstract: A boundary mode localized on one side of a finite-size lattice can tunnel to the opposite side which results in unwanted couplings. Conventional wisdom tells that the tunneling probability decays exponentially with the size of the system which thus requires many lattice sites before eventually becoming negligibly small. Here we show that the tunneling probability for some boundary modes can apparently vanish at specific wavevectors. Thus, similar to bound states in the continuum, a boundary mode can be completely trapped within very few lattice sites where the bulk bandgap is not even well-defined. More intriguingly, the number of trapped states equals the number of lattice sites along the normal direction of the boundary. We provide two configurations and validate the existence of this peculiar finite barrier-bound state experimentally in a dielectric photonic crystal at microwave frequencies. Our work offers extreme flexibility in tuning the coupling between localized states and channels as well as a new mechanism that facilitates unprecedented manipulation of light.

DOI: 10.1038/s41377-024-01417-1

Source: https://www.nature.com/articles/s41377-024-01417-1