We show that the resistance of the ν = 5/2 quantum Hall state, confined to an interferometer, oscillates with the magnetic field consistent with an Ising-type non-Abelian state. In three quantum Hall interferometers of different sizes, resistance oscillations at ν = 7/3 and integer filling factors have the magnetic field period expected if the number of quasiparticles contained within the interferometer changes so as to keep the area and the total charge within the interferometer constant. Under these conditions, an Abelian state such as the (3, 3, 1) state would show oscillations with the same period as at an integer quantum Hall state. However, in an Ising-type non-Abelian state there would be a rapid oscillation associated with the "even-odd effect" and a slower one associated with the accumulated Abelian phase due to both the Aharonov-Bohm effect and the Abelian part of the quasiparticle braiding statistics. Our measurements at ν = 5/2 are consistent with the latter.

We present a concept and experimental proof of principle for split-gate devices for indirect excitons (IXs). The split-gate forms a narrow channel, a point contact, for IX current. Control of IX flow through the split-gate with both gate voltage and excitation power is demonstrated.

The polariton-polariton interaction strength is an important parameter for all kinds of applications using the nonlinear properties of polaritons, such as optical switching and single-photon blockade devices. In this paper, we review and compare the results of a series of experiments on polariton-polariton interactions in GaAs/AlxGa1-xAs microcavity polariton structures and present an updated analysis of these experiments. We show that not just the energy shift of the spectral lines but also the results of measurements sensitive to the polariton scattering rate are important for the calibration of the interaction parameter at low excitation density. We find that when adjustments are made to correct for recent understanding of the experiments, the value of the interaction parameter at low density is lower than previous reported, but still significantly higher than theoretically predicted.

Exciton-polaritons are mixed light-matter particles offering a versatile solid state platformto study many-body physical effects. In this work, we demonstrate an electrically controlled polariton laser, in a compact, easy-to-fabricate and integrable configuration, based on a semiconductor waveguide. Interestingly, we show that polariton lasing can be achieved in a system without a global minimum in the polariton energy-momentum dispersion. The cavity modes for the laser emission are obtained by adding couples of specifically designed diffraction gratings on top of the planar waveguide, forming an in-plane Fabry-Perot cavity. It is due to the waveguide geometry that we can apply a transverse electric field to finely tune the laser energy and quality factor of the cavity modes. Remarkably, we exploit the system sensitivity to the applied electric field to achieve an electrically controlled population of coherent polaritons. The precise control that can be reached with the manipulation of the grating properties and of the electric field provides strong advantages to this device in terms of miniaturization and integrability, two main features for the future development of coherent sources for polaritonic technologies.

Exciton-polaritons are hybrid light-matter states that arise from strong coupling between an exciton resonance and a photonic cavity mode. As bosonic excitations, they can undergo a phase transition to a condensed state that can emit coherent light without a population inversion. This aspect makes them good candidates for thresholdless lasers, yet short exciton-polariton lifetime has made it difficult to achieve condensation at very low power densities. In this sense, long-lived symmetry-protected states are excellent candidates to overcome the limitations that arise from the finite mirror reflectivity of monolithic microcavities. In this work we use a photonic symmetry-protected bound state in the continuum coupled to an excitonic resonance to achieve state-of-the-art polariton condensation threshold in a GaAs/(Al,Ga)As waveguide. Most important, we show the influence of fabrication control and how surface passivation via atomic layer deposition provides a way to reduce exciton quenching at the grating sidewalls.