Observation of custodial chiral symmetry in memristive topological circuits

Abstract The concept of custodial symmetry, a residual symmetry that protects physical observables from large quantum corrections, has been a cornerstone of high-energy physics. In classical engineered systems, however, experimental realization and observation of its classical analog have remained unexplored. Building on recent theoretical work (2022 Phys. Rev. Lett. 128 097701), we report the first experimental observation of a classical analog of custodial chiral symmetry in a memristive Su–Schrieffer–Heeger (SSH) circuit. We provide direct experimental evidence for custodial symmetry by measuring the correction to the Lagrangian. This Lagrangian correction, which mimics a mass term in field theory, vanishes smoothly as the perturbation is reduced. We also demonstrate that topological edge states in the memristive SSH circuit remain localized at the boundary, consistent with custodial chiral symmetry. This work opens new avenues for emulating field-theoretic symmetries and nonlinear dynamics in memristive platforms.