Topolectrical-circuit realization of topological corner modes

By Stefan Imhof, C. Berger, F. Bayer, J. Brehm, L. Molenkamp, T. Kießling, F. Schindler, Ching Hua Lee, M. Greiter, Titus Neupert and 1 more. Nature Physics, 2017

1,029 citations recorded by the source corpus.

Quantized electric quadrupole insulators have recently been proposed as novel quantum states of matter in two spatial dimensions. Gapped otherwise, they can feature zero-dimensional topological corner mid-gap states protected by the bulk spectral gap, reflection symmetries and a spectral symmetry. Here we introduce a topolectrical circuit design for realizing such corner modes experimentally and report measurements in which the modes appear as topological boundary resonances in the corner impedance profile of the circuit. Whereas the quantized bulk quadrupole moment of an electronic crystal does not have a direct analogue in the classical topolectrical-circuit framework, the corner modes inherit the identical form from the quantum case. Due to the flexibility and tunability of electrical circuits, they are an ideal platform for studying the reflection symmetry-protected character of corner modes in detail. Our work therefore establishes an instance where topolectrical circuitry is employed to bridge the gap between quantum theoretical modelling and the experimental realization of topological band structures.The realization of a two-dimensional quadrupole topological insulator—featuring gapless corner states but an otherwise insulating bulk and edge—establishes electrical circuits as a versatile platform for implementing topological band structures.

Subfields: Atomic and Molecular Physics, and Optics, Materials Chemistry, Physical and Theoretical Chemistry

View Paper: https://www.semanticscholar.org/paper/572699da195802278430b0919803211b337cbf65

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Citations in the corpus

Higher-order non-Hermitian skin effect (2020, background): “[21] S.”
Quantization of fractional corner charge in Cn -symmetric higher-order topological crystalline insulators (2018, background): “[74] Stefan Imhof, Christian Berger, Florian Bayer, Johannes Brehm, Laurens W.”
Observation of second-order topological insulators in sonic crystals (2018, background): “Recently, by gapping out the edge states of topological insulators, HOTIs are created, where robust corner or hinge states emerge in the edge gap due to topological mechanisms [24-35].”
Roadmap on topological photonics (2022, background): “Other instances of topological phases that were first (or simultaneously) experimentally realized using photonics include quantum anomalous Hall insulators [6], Floquet topological insulators (FTIs) [7, 15, 16], higher-order topological insulators [17, 18], and topological Anderson insulators [19].”