Optical studies of a two-dimensional electron system in a cavity: quantum Hall polaritons
Light-matter interaction has played a central role in understanding and engineering new states of matter. Reversible coupling of excitons and photons enabled groundbreaking results in condensation and superfluidity of nonequilibrium quasiparticles with a photonic component. In this work, we combine the physics of correlated many-body states in a two-dimensional electron system with the methods of cavity quantum electrodynamics. By coupling the cavity photon of an AlGaAs based DBR micro-cavity structure to optical inter-band excitations of a 20 nm GaAs quantum well we observe the emergence of novel many-body polariton modes. In the presence of a magnetic field, polaritons show distinct signatures of integer and fractional quantum Hall ground states. We use the strong coupling of the cavity mode to bound trion states of inter-Landau level transitions to perform the spectroscopy of many-body correlated states in the quantum Hall regime. These quantum Hall polaritons provide a direct way to study the spin-polarization of quantum Hall states by measuring the polarization dependent normal-mode splitting. Our technique is also well suited to study the compressibility of the electron system and constitutes a powerful method to complement transport spectroscopy with the advantages of a minimally invasive local probe.
Host: Luis A. Orozco