Higher-Order Dirac Sonic Crystals
Higher-Order Dirac Sonic Crystals
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高阶狄拉克声波晶体
DOI：
10.1103/physrevlett.127.146601
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发表时间：
2021-09-28
影响因子：
8.6
通讯作者：
Qiu, Chunyin
中科院分区：
文献类型：
--
作者：
Qiu, Huahui;Xiao, Meng;Qiu, Chunyin
发现物质的新拓扑相是基础物理学和材料科学的一个重要主题。狄拉克半金属为探索对称破缺下的拓扑相变提供了一个特殊的平台。最近的理论研究表明，三维狄拉克半金属可以拥有令人着迷的铰链态，这是一种以前未知的高阶拓扑表现。然而，其在实验中的实现尚未实现。在这封信中，我们提出了一个最小模型来构造受 C-6 upsilon 对称性保护的无自旋高阶狄拉克半金属。通过打破不同的对称性，该母相转变为各种新颖的拓扑相，包括高阶拓扑绝缘体、高阶Weyl半金属和高阶节环半金属。此外，我们首次通过实验在声波晶体中实现了这种前所未有的高阶拓扑相，并通过动量空间光谱和实空间可视化对所需铰链态进行了明确的观察。我们的发现可能为操纵声音和光等经典波提供新的机会。
Discovering new topological phases of matter is a major theme in fundamental physics and materials science. Dirac semimetal provides an exceptional platform for exploring topological phase transitions under symmetry breaking. Recent theoretical studies have revealed that a three-dimensional Dirac semimetal can harbor fascinating hinge states, a higher-order topological manifestation not known before. However, its realization in experiment is yet to be achieved. In this Letter, we propose a minimum model to construct a spinless higher-order Dirac semimetal protected by C-6 upsilon symmetry. By breaking different symmetries, this parent phase transitions into a variety of novel topological phases including higher-order topological insulator, higher-order Weyl semimetal, and higher-order nodal-ring semimetal. Furthermore, for the first time, we experimentally realize this unprecedented higher-order topological phase in a sonic crystal and present an unambiguous observation of the desired hinge states via momentum-space spectroscopy and real-space visualization. Our fmdings may offer new opportunities to manipulate classical waves such as sound and light.