Observation of non-Hermiticity-induced unpolarized Landau levels in honeycomb circuit networks

Landau levels play a crucial role in exploring fundamental phenomena of condensed-matter physics. Recently, a new paradigm for generating Landau levels by means of non-Hermiticity has been proposed. Notably, the zeroth Landau level states here are unpolarized, unlike the sublattice-polarized states in Hermitian Dirac systems. However, due to the challenges of implementing spatially varying dissipation and large gain-loss terms, the experimental demonstration of such Landau level has remained elusive. Here, we present an experimental observation in honeycomb circuit networks. Specifically, we construct a circuit lattice consisting of two types of non-Hermitian configurations to realize a large pseudomagnetic field. Through measuring the admittance spectrum and voltage responses, we successfully observe the unpolarized zeroth Landau level and Hall-like edge states in the non-Hermitian Dirac circuit lattice. Extending the system to a synthetic 3D non-Hermitian Weyl circuit, we further observe the non-Hermiticity-induced chiral LLs and surface modes. Our work paves the way for studying non-Hermitian quantum Hall physics and may be useful for designing novel topological devices.