Corner responses show a new quantum phase in RLC circuits

Wenxue He, Chen Wang, Fan Yang, and Hechen Ren of Tianjin University have experimentally demonstrated a new quantum phase within a square-octagon RLC circuit initially functioning as a gapped trivial insulator. The researchers introduced on-site loss to the circuit using patterned grounding resistors, maintaining fixed conservative couplings to induce a quadrupole topological transition. Impedance spectroscopy and spatial maps then revealed corner-localized responses consistent with the predicted phase, connecting dissipation-driven topology to observable boundary behavior in RLC circuits. These results offer a new way to control topology through dissipation. A square-octagon circuit, constructed from standard electronic components, has demonstrated a loss-induced quadrupole topology, starting from a configuration known as a gapped trivial insulator. The design frequency of the circuit was established at approximately 0.777 MHz, using capacitors of 100 nanofarads and 10 nanofarads, combined with 200 nanohenry inductors, to achieve a specific hopping ratio of 0.1, characteristic of the initial quadrupole phase. Measurements of the circuit without intentional resistive grounding served as a baseline for comparison with the loss-induced experiments. Further experiments shifted the circuit’s parameters to a gapped trivial…