Electronic Hong Ou Mandel interferences to unveil the 2/3 fractional quantum Hall edge channel dynamics

Electronic Hong Ou Mandel (HOM) current noise interferometry has revealed the anyonic statistics of fractionally charged anyons (e/3 or e/5) in Fractional Quantum Hall (FQH) phases at filling factors ν=1/3 and ν=2/5. However, hole-conjugated phases with filling factors ½ < ν < 1 host both charge and neutral edge modes, making them sensitive to disorder and challenging for interferometry. Current understanding of these modes largely stems from DC transport measurements, offering limited insight into their dynamics. Going beyond this limited information, we introduce time-domain electronic HOM and Photon-Assisted-Shot-Noise (PASN) measurements at ν=2/3, elucidating the dynamics of the ν=2/3 edge modes. PASN reveals damping in downstream charge modes, consistent with the inability of upstream neutral modes to propagate beyond the micrometer-scale disorder-induced charge equilibration length. Using PASN’s fractional Josephson relation, we confirm the e/3 tunneling charge of the ν=2/3 state. Time-resolved HOM interference demonstrates broadening of picosecond charge pulses, consistent with damped charge modes and non-propagating neutral modes. These findings suggest a need to revisit the role of neutral modes in hole-conjugate FQH phases and indicate limited potential for robust HOM interferometry beyond micrometer scales. Our approach may extend to investigate a variety of complex FQH states, including non-abelian anyons, hosting neutral modes