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 anyonic statistics in Fractional Quantum Hall (FQH) states at ν = 1/3 and 2/5. However, hole-conjugate phases (½ < ν < 1), like ν = 2/3, host both charge and neutral edge modes, are disorder-sensitive, and pose challenges for interferometry. We present time-domain HOM and Photon-Assisted Shot Noise (PASN) measurements at ν = 2/3 to probe edge mode dynamics and tunneling charge. Using PASN's fractional Josephson relation, we measure an e/3 tunneling charge and show that DC shot noise overestimates charge below ~100 mK. PASN reveals damping of downstream charge modes due to limited propagation of upstream neutral modes beyond a micrometer-scale equilibration length. Time-resolved HOM measurements confirm picosecond pulse broadening. These results suggest revisiting the neutral mode status, highlight the limitations of HOM interferometry in hole-conjugate phases and provide a path to explore complex FQH states that host neutral or non-Abelian modes. The dynamics of hole-conjugated fractional quantum Hall states is poorly understood due to the limitations of current experimental probes. Here the authors study the high-frequency dynamics of edge modes at filling factor 2/3, precisely identifying the tunneling charge and damping of constituent charge modes.