Interferometric measurement of filling factor 5/2 quasiparticle charge

Abstract
A standing problem in low dimensional electron systems is the nature of the 5/2 fractional quantum Hall state, with its elementary excitations a focus for both elucidating the state's properties but also as candidates in methods to perform topological quantum computation. Interferometric devices may be employed to try to manipulate and measure quantum Hall edge excitations: here we use a small area, high sensitivity surface gate defined edge state interferometer designed to observe quasiparticle interference effects in ultra-high mobility GaAs heterostructures. Oscillations consistent in detail with the Aharanov-Bohm effect are observed for integer quantum Hall states (filling factor 2) and for fractional quantum Hall states (filling factor 5/3) with appropriate periods corresponding to their respective charges and magnetic field positions. Using these findings for charge metrics, at 5/2 filling factor and at lowest temperatures periodic transmission through the device consistent with quasiparticle charge e/4 is observed. The device sensitivity is sufficient to observe temperature evolution of the 5/2 quasiparticle charge: at low temperatures oscillations predominantly indicate charge e/4, changing to e/2 at higher temperatures. These studies demonstrate the general capacity to perform interferometry on 5/2 excitations and reveal properties of the different elementary excitation charges at 5/2 that are important for future work in applying this system to topological quantum computation.