Study of exciton-polariton spin dynamics

• Published in: Applied physics letters 2004-11, Vol.85 (22), p.5263-5265
• Main Authors: Soleimani, H. Rahimpour, Cronenberger, S., Crégut, O., Likforman, J.-P., Gallart, M., Ostatnicky, T., Gilliot, P., Hönerlage, B.
• Format: Article
• Language: English
• Subjects: Condensed Matter; Other; Physics
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.1830080

We study the relaxation dynamics of spin-polarized exciton-polaritons using a technique in a pump-probe configuration: According to their total angular momentum, exciton-polaritons can be excited by circularly polarized light of either σ + or σ − helicities. In addition, a bound state of two excitons may exist to which the transition is only allowed when using two photons of opposite helicities. After excitation by a pump pulse of σ + helicity, additional polaritons from a probe pulse of σ − helicity may be absorbed to excite biexcitons, while absorption of those with σ + helicity becomes possible only after a spin-flip process. It is characterized by a time-constant τ s , which can be determined by a time-resolved study of the induced transmission changes at the exciton-biexciton transition. We demonstrate this method using bulk CuCl, in which the biexciton binding energy is large and in which effects due to polariton propagation can be nicely evidenced. We thus identify a spectral region where the spin-flip process is dominating, which is situated just below the polariton bottleneck.