声表面波声子晶体中声拓扑态的理论及实验研究

To discover and utilize the topologically ordered states, such as quantum Hall states and quantum spin Hall states, is one of the most intriguing advance in physics over the last decade. Although these novel states were first observed in Fermi electronic systems, it is now expanding extensively to other systems, like bosonic photons and phonons, with a rapid expansion. The essential reason is the backscattering-immune edge states, for transportation of bosonic photons/phonons does not need any potential gradients or spin pumps like fermi electrons. Thereby it offers a reflection-free transportation with unparalleled tolerance towards any “non-magnetic” defects and fabrication imperfections, opening up a new era of large-scale photonic/phononic circuits. . Surface acoustic waves (SAWs), i.e., phonons in semi-infinite solid-state surface, can also benefit from topologically protected transport. Indeed, SAWs have several unique advantages in electro-acoustic information processing, including extremely low transmission losses, much smaller sizes of devices and stronger phonon–phonon interactions in comparison with other systems. However, to realize topologically-protected transport in SAWs, one must overcome some long-standing difficulties associated with symmetry and degeneracy inherent to elastic materials. Hence, though the topological phases in SAW systems have long been predicted, none has been practical realized so far. . In order to solve this key problem, this project will study the realization of topological phase transition in SAW system, especially for easy implementation and easy integration. Finally, we aim to develop a series of static and passive (without any external field) functional materials and prototyping devices where SAWs are immune to all fabrication imperfections and arbitrary corners with extreme low transmission losses.

近年来，拓扑态和拓扑相变问题成为凝聚态物理学前沿焦点。虽然该问题起源于费米电子系统，例如量子霍尔效应家族，却已全面快速被拓展到玻色子（如光/声）系统中。声表面波作为最具集成化器件优势的声学系统，若能在其中实现拓扑态和拓扑相变，将对现有的声表面波器件带来重大的影响和广泛的应用。但由于数个关键问题的存在，声表面波系统的拓扑效应研究十分具有挑战。本项目拟针对声表面波系统拓扑态展开理论与实验研究，发展声表面波声子晶体的拓扑能带理论，设计非平庸的拓扑能带结构，实现基于压电材料的声表面波拓扑绝缘体，并最终拟研制出一系列被动的（无源无外场的）、传输对缺陷及任意转角免疫的、具有极低传输损耗的新型声表面波功能材料与原型器件。

近年来，拓扑态和拓扑相变问题成为凝聚态物理学前沿焦点。虽然该问题起源于费米电子系统，例如量子霍尔效应家族，却已全面快速被拓展到玻色子（如光/声）系统中。声表面波作为最具集成化器件优势的声学系统，若能在其中实现拓扑态和拓扑相变，将对现有的声表面波器件带来重大的影响和广泛的应用。但由于数个关键问题的存在，声表面波系统的拓扑效应研究十分具有挑战。本项目针对声表面波系统拓扑态展开理论与实验研究，经过三年的研究，全面发展了基于Rayleigh波与Lamb波的声表面波声子晶体的拓扑能带理论，设计非平庸的拓扑能带结构，实现了基于压电材料及非压电材料的声表面波拓扑绝缘体，并最终研制出了一系列相较传统器件具有性能优势的、被动的（无源无外场的）、传输对缺陷及任意转角免疫的、具有极低传输损耗的新型声表面波功能材料与原型器件。与此同时，项目负责人在该项目方向指导硕士、博士研究生数人；发表包括Nature Communications、National Science Review及Physical Review Applied在内的各类论文共计12篇。