Luogo: Polo Ferrari 1 via Sommarive 5 Povo - Room A208
dr . Martin Kroner
Strong coupling of excitons in a semiconductor quantum well (QW) to a microcavity mode leads to the formation of quasiparticles called cavity exciton polaritons. While polaritons acquire a finite matter character, their mutual interactions as well as their interaction to externally applied fields remain weak. In order to overcome this limitation we introduce itinerant electrons into the QW. The elementary optical excitations of such a two-dimensional electron system (2DES) embedded in an optical cavity are exciton polarons where the excitons are dressed by Fermi-sea electron hole pair excitations to form Fermi polarions. In this regime, the light-matter coupling strength is sensitive to the electronic ground state, which can be modified in the presence of electric and magnetic fields, particularly when the electrons occupy integer and fractional Quantum Hall states.
We perform linear and nonlinear spectroscopy to explore polariton-polariton interactions in the fractional quantum Hall regime, and we find more than an order of magnitude increased interactions in the case of filling factor 2/5. Further, by applying an in-plane electric field to the 2DES, we can introduce an electron gradient in the sample which generates an accelerating potential for polaron polaritons. The resulting electrically driven polariton drift can be further controlled by a perpendicular magnetic field. We find that close to filling factor 1 the accelerating potential for the polaritons becomes spin selective and leads to an effective spin current.
dr. Iacopo Carusotto