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Higher-order topological insulators have been recently proposed as unprecedented quantum states of matter. In two spatial dimensions, they incorporate quantized electric quadrupole insulators, which feature zero-dimensional topological corner midgap states. These states are protected by the bulk gap, reflection symmetries, and a spectral symmetry, while their edges are gapped. Although such novel topological phases are often hard to come by in real materials, there are various analogue platforms that enable us to realize the corresponding band theory concepts in classical systems. I will talk about how we developed and measured a topolectrical circuit design for a quadrupole insulator, the midgap states of which manifest themselves as topological boundary resonances in the corner impedance profile of the circuit. This establishes an instance where topolectrical circuitry is employed to bridge the gap between quantum theoretical modeling and the experimental realization of topological band structures.

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Frank Schindler, University of Zurich
Seminarraum Kernphysik
Contact: Finn Lasse Buessen