Nanomechanical topological insulators with an auxiliary orbital degree of freedom
Nanomechanical topological insulators with an auxiliary orbital degree of freedom
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DOI：
10.1038/s41565-021-00868-6
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发表时间：
2021-04-19
影响因子：
38.3
通讯作者：
Sun, Xiankai
中科院分区：
文献类型：
--
作者：
Ma, Jingwen;Xi, Xiang;Sun, Xiankai
拓扑绝缘体具有防止无序的边缘状态，可以在实际材料中实现，也可以在基于光学、声学或机械特性的合成材料中实现。除了自旋，轨道自由度现在还为操纵拓扑相提供了一个额外的手柄。离散自由度，如自旋和轨道，提供了操纵电子、光子和声子的工具。拓扑绝缘体激发了人们对凝聚态物理、光学、声学和力学的浓厚兴趣，通常集中在自旋自由度上。然而，轨道自由度是晶体的另一个基本属性，但在拓扑绝缘体中很少被研究。在这里，我们演示了具有辅助轨道自由度的拓扑绝缘体在纳米机械平台上的应用。我们实现了不同拓扑边缘状态之间的绝热转变，这构成了集成电路适应不同拓扑边缘通道的关键功能。在一维边缘态的基础上，利用轨道自由度进一步构造了零维狄拉克涡旋态。这些纳米机械Dirac-涡旋态表现出很强的二阶和三阶非线性。我们的结果引入了轨道自由度作为一种替代手段来操纵集成平台上的拓扑相变。
Topological insulators possess edge states protected from disorder and can be realized in real materials as well as in synthetic materials based on optical, acoustic or mechanical characteristics. In addition to the spin, the orbital degree of freedom now provides an extra handle for manipulating topological phases.Discrete degrees of freedom, such as spin and orbital, provide a tool to manipulate electrons, photons and phonons. Topological insulators have stimulated intense interests in condensed-matter physics, optics, acoustics and mechanics, usually with a focus on the spin degree of freedom. However, the orbital degree of freedom constitutes another fundamental attribute in crystals, but has seldom been investigated in topological insulators. Here, we demonstrate topological insulators with an auxiliary orbital degree of freedom on a nanomechanical platform. We realize an adiabatic transition between distinct topological edge states, which constitutes a crucial functionality for integrated circuits accommodating distinct topological edge channels. Beyond the one-dimensional edge states, we further construct zero-dimensional Dirac-vortex states using the orbital degree of freedom. These nanomechanical Dirac-vortex states exhibit strong second-order and third-order nonlinearities. Our results introduce the orbital degree of freedom as an alternative means to manipulate the topological phase transition on an integrated platform.