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 nu = 8/3, nu = 5/2, and nu = 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 nu = 7/3 and nu = 8/3 states, we found a quasiparticle charge e = 1/3 and an upstream neutral mode only in nu = 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 nu = 7/3 state also proves that edge reconstruction was not present in the nu = 7/3 state, suggesting its absence also in nu = 5/2 state, and thus may provide further support for the non-Abelian anti-Pfaffian nature of the nu = 5/2 state.