Marco Abbarchi

Direct Observation of Dirac Cones and a Flatband in a Honeycomb Lattice for Polaritons

Two-dimensional lattices of coupled micropillars etched in a planar semiconductor microcavity offer a workbench to engineer the band structure of polaritons. We report experimental studies of honeycomb lattices where the polariton low-energy dispersion is analogous to that of electrons in graphene. Using energy-resolved photoluminescence, we directly observe Dirac cones, around which the dynamics of polaritons is described by the Dirac equation for massless particles. At higher energies, we observe p orbital bands, one of them with the nondispersive character of a flatband. The realization of this structure which holds massless, massive, and infinitely massive particles opens the route towards studies of the interplay of dispersion, interactions, and frustration in a novel and controlled environment.

Macroscopic quantum self-trapping and Josephson oscillations of exciton polaritons

The Josephson effects that arise when two quantum states are coupled through a barrier are difficult to observe in optical systems because photon–photon interactions are so weak. Researchers have now demonstrated an optical realization of two such phenomena—macroscopic self-trapping and Josephson oscillations—using polariton condensates in overlapping microcavities.

Spin-Orbit Coupling for Photons and Polaritons in Microstructures

We use coupled micropillars etched out of a semiconductor microcavity to engineer a spin-orbit Hamiltonian for photons and polaritons in a microstructure. The coupling between the spin and orbital momentum arises from the polarization-dependent confinement and tunneling of photons between adjacent micropillars arranged in the form of a hexagonal photonic molecule. It results in polariton eigenstates with distinct polarization patterns, which are revealed in photoluminescence experiments in the regime of polariton condensation. Thanks to the strong polariton nonlinearities, our system provides a photonic workbench for the quantum simulation of the interplay between interactions and spin-orbit effects, particularly when extended to two-dimensional lattices.

Control of Polariton Patterns in Semiconductor Microcavities

Polaritons in semiconductor microcavities can form patterns analogous to conventional Turing patterns, including two-spot and hexagon far field patterns. We present theoretical concepts of pattern formation and control, together with experimental observations.

Macroscopic Self-trapping and Non-linear Oscillations in Coupled PolaritonCondensates

Exciton-polaritons are mixed light-matter particles in semiconductor microcavities. They form boson condensates with striking properties like superfluidity, nucleation of quantized vortices and oblique dark solitons, or monopole-like excitations when their spin is taken into account.