Characterizing Neutral Modes of Fractional States in the Second Landau Level

Fractionally charged quasiparticles, which obey non-Abelian statistics, were predicted to exist in the ν=8/3, ν=5/2, and ν=7/3 fractional quantum Hall states (in the second Landau level). Here we present measurements of charge and neutral modes in these states. For both ν=7/3 and ν=8/3 states, we found a quasiparticle charge $e=1/3$ and an upstream neutral mode only in ν=8/3---excluding the possibility of non-Abelian Read-Rezayi states and supporting Laughlin-like states. The absence of an upstream neutral mode in the ν=7/3 state also proves that edge reconstruction was not present in the ν=7/3 state, suggesting its absence also in ν=5/2 state, and thus may provide further support for the non-Abelian anti-Pfaffian nature of the ν=5/2 state.