Interacting Polaron-Polaritons

Abstract

Two-dimensional semiconductors provide an ideal platform for exploration of linear exciton and polariton physics, primarily due to large exciton binding energy and strong light-matter coupling. These features, however, generically imply reduced exciton-exciton interactions, hindering the realization of active optical devices such as lasers or parametric oscillators. Here, we show that electrical injection of itinerant electrons into monolayer molybdenum diselenide allows us to overcome this limitation: dynamical screening of exciton-polaritons by electrons leads to the formation of new quasiparticles termed polaron-polaritons that exhibit unexpectedly strong interactions as well as optical amplification by Bose-enhanced polaron-electron scattering. To measure the nonlinear optical response, we carry out timeresolved pump-probe measurements and observe polaron-polariton interaction enhancement by a factor of 50 (0.5 μeV μm 2) as compared to exciton-polaritons. Concurrently, we measure a spectrally integrated transmission gain of the probe field of ≳2 stemming from stimulated scattering of polaron-polaritons. We show theoretically that the nonequilibrium nature of optically excited quasiparticles favors a previously unexplored interaction mechanism stemming from a phase-space filling in the screening cloud, which provides an accurate explanation of the strong repulsive interactions observed experimentally. Our findings show that itinerant electron-exciton interactions provide an invaluable tool for electronic manipulation of optical properties, demonstrate a new mechanism for dramatically enhancing polariton-polariton interactions, and pave the way for realization of nonequilibrium polariton condensates.

Creation of bipartite steering correlations by a fast damped auxiliary mode

“…Of particular interest is the possibility to achieve quantum steering in macroscopic systems. For this reason, considerable attention has been devoted to optomechanical systems, where the dynamics of the macroscopic mechanical mode of the oscillating mirror can be controlled through the coupling to an optical cavity mode [37][38][39][40][41][42][43].…”

“…To quantify steering, we adopt the Reid criterion [60], which is applicable to non-idealized Gaussian continuous variable systems, i.e. for dissipative Gaussian systems which decay to decohered mixed Gaussian states [6,38,50,[54][55][56][57][58][59]. We adiabatically eliminate the fast damped mode which enables us to obtain modified equations of motion for the operators of the remaining two modes.…”

Material Makes Photons Bulky

“…by Iacopo Carusotto 1 N onlinear effects will be a crucial ingredient of future optical quantum information platforms. By allowing different information-carrying photons to interact, these effects can be useful for performing basic tasks like shifting the photons' color, modifying their statistics, and inducing entanglement between them.…”

“…Nonlinear processes are ubiquitous in laser optics, but in typical materials they are too inefficient to have a measurable effect at the single-photon level, as would be required for advanced quantum optics applications. Now, Li Bing Tan of the Swiss Federal Institute of Technology (ETH) in Zurich and co-workers report on a novel way to boost the optical nonlinearity of a medium [1]. Their idea is to couple, Figure 1: Sketch of the mechanism used by Tan et al to boost optical nonlinearity [1].…”

“…Now, Li Bing Tan of the Swiss Federal Institute of Technology (ETH) in Zurich and co-workers report on a novel way to boost the optical nonlinearity of a medium [1]. Their idea is to couple, Figure 1: Sketch of the mechanism used by Tan et al to boost optical nonlinearity [1]. Photons (magenta balls) couple strongly to excitons (blue balls) to form polariton quasiparticles.…”