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Strong and weak coupling limits in optics of quantum well excitons

Creatore, Celestino and Ivanov, Alexei L. 2008. Strong and weak coupling limits in optics of quantum well excitons. Physical Review B 77 (7) , 075324. 10.1103/PhysRevB.77.075324

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A transition between the strong (coherent) and weak (incoherent) coupling limits of resonant interaction between quantum well (QW) excitons and bulk photons is analyzed and quantified as a function of the incoherent damping rate γx caused by exciton-phonon and exciton-exciton scatterings. For confined QW polaritons, a second, anomalous, γx-induced dispersion branch arises and develops with increasing γx. In this case, the strong-weak coupling transition is attributed to γx=γxtr or γ̃xtr, when the intersection of the normal and damping-induced dispersion branches occurs either in {k∥,Im[ω],Re[ω]} coordinate space (in-plane wave vector k∥ is real) or in {ω,Im[k∥],Re[k∥]} coordinate space (frequency ω is real), respectively. For the radiative states of QW excitons, i.e., for radiative QW polaritons, the transition is described as a qualitative change of the photoluminescence spectrum at grazing angles along the QW structure. We show that the radiative corrections to the QW exciton states with in-plane wave vector k∥ approaching the photon cone, i.e., at k∥→k0=(ω0√εb)∕(ℏc) (εb is the background dielectric constant), are universally scaled by the energy parameter (Γ02ω0)1∕3 with Γ0 the intrinsic radiative width and ω0 the exciton energy at k∥=0, rather than diverge. Similarly, the strong-weak coupling transition rates γxtr and γ̃xtr are also proportional to (Γ02ω0)1∕3. The numerical evaluations are given for a GaAs single quantum well with realistic parameters: Γ0=45.5 μeV and (Γ02ω0)1∕3≈1.5 meV.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Subjects: Q Science > QC Physics
Publisher: American Physical Society
ISSN: 1098-0121
Last Modified: 03 Feb 2020 00:24

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