Recently, the topological states in electric circuits have attracted a great deal of attention, and they have formed the basis of the field of so-called topoelectrical circuits. We realize a second-order topological electric circuit with capacitors and inductors, and we observe the corner states that exist in the bulk gap, the continuum of bulk modes, and the dependence on the corner shapes by measuring the resonance peaks of the corner impedance. More importantly, we broaden the second-order topological circuit to the non-Hermitian region by adding resistors. Interestingly, the non-Hermiticity tunes the amplitude of the corner impedance; however, it has no effect on the topological properties. Our system provides a highly tunable platform in which to explore the intriguing topological properties of higher-order topological insulators.

中文翻译：

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观察二阶拓扑电路中的角状态

近来，电路中的拓扑状态引起了极大的关注，并且它们已经成为所谓的拓扑电路领域的基础。我们用电容器和电感器实现了二阶拓扑电路，并且通过测量角阻抗的谐振峰值，观察了存在于体隙中的角状态，体模式的连续性以及对角形状的依赖性。更重要的是，通过添加电阻器，我们将二阶拓扑电路扩展到了非Hermitian区域。有趣的是，非赫米蒂尼度会调节转角阻抗的幅度。但是，它对拓扑特性没有影响。我们的系统提供了一个高度可调的平台，可在其中探索高阶拓扑绝缘子的有趣拓扑特性。