Influence of a nonradiative reservoir on polariton spin multistability

Abstract

In this work, we study the influence of the excitation conditions on power-dependent spin switching and spin multistability of exciton polaritons in planar semiconductor microcavities. We obtain experimental evidence for the influence of a reservoir of nonradiative states which make a determining contribution to the dynamics of polaritons. While the spinor Gross-Pitaevskii equation (SGPE) fails in reproducing some critical experimental trends, an extended set of equations including a nonradiative reservoir allows us to reproduce the experiments quantitatively. We find that the energy renormalization of the exciton field due to the reservoir is crucial to describe power-dependent spin switching. The reservoir is also responsible for the effective repulsive interactions between polaritons of opposite spin obtained in the framework of the SGPE. Two important parameters, the coupling of the spinor polariton fields to the reservoir and the decay of the reservoir, are determined experimentally. We present indications that the reservoir originates from the formation of biexcitons and is constituted of localized exciton states.

Nonlinear route to intrinsic Josephson oscillations in spinor cavity-polariton condensates

“…Thus, at the pulse tail, we deal with a freely decaying rather than pumped polariton condensate. It only can be slightly fed by a long-lived excitonic reservoir excited when the pump was strong [23,29,37,38]; however, this effect cannot be pronounced in our system where the pump is comparatively short term and acts far below the exciton level.…”

Spatial multistability induced by cross interactions of confined polariton modes

“…Finally, the external driving field of energy E l which pumps each photon mode is defined as f ext = √ I 0 exp(−iE l t/ ). Equations (4) can be understood as a multimode generalization of the Gross-Pitaevskii equation in the exciton-photon basis [33,69]. These equations include the usual population exciton-exciton self-interaction terms g ii but also cross-interaction terms g ij that couple the exciton polarization of state i with the population of state j .…”

“…This effect is caused by the population of one polariton spin state that can induce a blue shift in the orthogonally polarized polariton branch [33]. Then, the overall competition between the excitation laser polarization, spinor interactions, and cavity anisotropy dictates the possible outcome of the multistability [28,31,33].…”

Relaxation Oscillations in the Formation of a Polariton Condensate

“…One component that is seldom considered in details is the exciton reservoir. This, however, often plays an important role, even under resonant excitation [11,12], and in particular when it comes to polariton relaxation and condensation.We will show here how a polariton condensate formed by non-resonant excitation, in a confined region of space of a few micron squared, can exhibit marked oscillations of its population. While many oscillatory behaviours have been observed [13,14] or predicted [15] in the polariton literature, relating them to coherent and/or quantum phenomena, we report semi-classical oscillations due to the interplay between reservoir feeding and Bose stimulation.…”