Half-quantized Hall plateaus in the confined geometry of graphene

Controlling quantum states in low-dimensional systems is a cornerstone of modern condensed matter physics, with far-reaching implications for quantum information technologies. Among these, two-dimensional materials under strong magnetic fields provide a rich arena for realizing exotic transport phenomena in confined geometries. We report the observation of half-quantized conductance plateaus at unconventional filling factors, including ν = 5/2, of non-topological origin, realized by a quantum point contact in monolayer graphene. The observed plateaus arise due to two distinct mechanisms: conventional charge equilibration between fractional quantum Hall edge states with different filling factors, and more unexpectedly, a novel process involving charge equilibration between fractional quantum Hall edge states and metallic reservoirs mediated by graphene’s zeroth Landau level. This work deepens the understanding of fractional quantum Hall states near metallic phases, challenging the circumstances under which quantized half-integer conductance can arise due to non-topological phenomena and offering new insights into the engineering of quantum devices. Two-dimensional materials under strong magnetic fields can demonstrate exotic transport phenomena in confined geometries. This paper observes half-quantized conductance plateaus at unconventional filling factors, including ν = 5/2, of non-topological origin, realized by a quantum point contact in monolayer graphene.