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We demonstrate operation of a small Fabry-Perot interferometer in which highly coherent Aharonov-Bohm oscillations are observed in the integer and fractional quantum Hall regimes. Using a novel heterostructure design, Coulomb effects are drastically suppressed. Coherency of edge mode interference is characterized by the energy scale for thermal damping, T0 = 206mK at ν = 1. Selective backscattering of edge modes originating in the N = 0, 1, 2 Landau levels allows for independent determination of inner and outer edge mode velocities. Clear Aharonov-Bohm oscillations are observed at fractional filling factors ν = 2/3 and ν = 1/3. Our device architecture provides a platform for measurement of anyonic braiding statistics. arXiv:1901.08452v1 [cond-mat.mes-hall]

Quantum Hall interferometers have been used to probe fractional charge and statistics of quasiparticles. We present measurements of a small Fabry–Perot interferometer in which the electrostatic coupling constants which affect interferometer behavior can be determined experimentally. Near the center of the ν = 1/3 state this device exhibits Aharonov–Bohm interference interrupted by a few discrete phase jumps, and Φ0 oscillations at higher and lower magnetic fields, consistent with theoretical predictions for detection of anyonic statistics. We estimate the electrostatic parameters KI and KIL by two methods: using the ratio of oscillation periods in compressible versus incompressible regions, and from finite-bias conductance measurements. We find that the extracted KI and KIL can account for the deviation of the phase jumps from the theoretical anyonic phase θa = 2π/3. At integer states, we find that KI and KIL can account for the Aharonov–Bohm and Coulomb-dominated behavior of different edge states.

We study low-frequency charge noise in shallow GaAs/AlGaAs heterostructures using quantum point contacts as charge sensors. We observe that devices with an Al2O3 dielectric between the metal gates and semiconductor exhibit significantly lower charge noise than devices with only Schottky gates and no dielectric. Additionally, the devices with Schottky gates exhibit drift over time toward lower conductance, while the devices with the dielectric drift toward higher conductance. Temperature-dependent measurements suggest that in devices with Schottky gates, noise is dominated by tunneling from the gates to trap sites in the semiconductor, and when this mechanism is suppressed by inclusion of a dielectric, thermally activated hopping between trap sites becomes the dominant source of noise.

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We investigate electronic structure theoretically in strained GaN/AlN quantum dots (QDs) with wurtzite (WZ) crystal structure. The QD electron energy levels are calculated using the finite element method (FEM) in the framework of effective mass approximation (EMA). We analyze the influence of strain and polarization to the electron energy levels and calculate electron energy levels with different dot sizes. It is shown that the strain dependent deformation potential and piezoelectric potential increase the electron energy levels and split the degenerate states. The electron energy levels decreases rapidly with increasing QD height, which is partly due to the confinement energy reduction. However, the piezoelectric field makes a more significant contribution.