Aharonov-Bohm interference in even-denominator fractional quantum Hall states

Position exchange of non-Abelian anyons affects the quantum state of their system in a topologically protected way¹. Their expected manifestations in even-denominator fractional quantum Hall (FQH) systems offer the opportunity to directly study their unique statistical properties in interference experiments². Here we present the observation of coherent Aharonov-Bohm interference at two even-denominator states in high-mobility bilayer-graphene-based van der Waals (vdW) heterostructures by using the Fabry-Pérot interferometry technique. Operating the interferometer at a constant filling factor, we observe an oscillation period corresponding to two flux quanta inside the interference loop, ΔΦ = 2Φ₀, at which the interference does not carry signatures of non-Abelian statistics. The absence of the expected periodicity of ΔΦ = 4Φ₀ may indicate that the interfering quasiparticles carry the charge $e^{*}=\frac{1}{2}e$ or that interference of $e^{*}=\frac{1}{4}e$ quasiparticles is thermally smeared. Notably, at two hole-conjugate states, we also observe oscillation periods of half the expected value, indicating interference of $e^{*}=\frac{2}{3}e$ quasiparticles instead of $e^{*}=\frac{1}{3}e$ . To investigate statistical phase contributions, we operated the Fabry-Pérot interferometer (FPI) with controlled deviations of the filling factor, thereby introducing fractional quasiparticles inside the interference loop. The resulting changes to the interference patterns at both half-filled states indicate that the extra bulk quasiparticles carry the fundamental charge $e^{*}=\frac{1}{4}e$ , as expected for non-Abelian anyons.