Electrostatic Measurements of Fractional Charge in the Second Landau Level

The fractional quantum Hall state at filling factor 5/2 is predicted to result from a BCS pairing instability in a Fermi sea of composite fermions. The resulting p-wave paired state would have the lucrative property of supporting non-Abelian braiding statistics which can be leveraged for decoherence-free quantum computation. A robust prediction of any theory involving pairing at half-integer filling in the quantum Hall regime is that quasiparticles should have charge e/4. Local compressibility measurements allow us to compare how quasiparticles charge disorder puddles at 7/3 and 5/2. From this comparison, we can extract the ratio of quasiparticle charges for these states. The value we obtain, 4/3, suggests a local charge of e/4 at 5/2 (assuming e/3 at 7/3). We additionally show that these e/4 quasiparticles can be pinned by disorder, a prerequisite for the interferometry measurements that may demonstrate non-Abelian braiding statistics.