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Switching the sign of photon induced exchange interactions in semiconductor microcavities with finite quality factors

G. Chiappe·E. Louis y E. V. Anda
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Abstract

We investigate coupling of localized spins in a semiconductor quantum dot embedded in a microcavity with a finite quality factor. The lowest cavity mode and the quantum dot exciton are coupled forming a polariton, whereas excitons interact with localized spins via exchange. The finite quality of the cavity Q is incorporated in the model Hamiltonian by adding an imaginary part to the photon frequency. The Hamiltonian, which treats photons, spins and excitons quantum mechanically, is solved exactly. Results for a single polariton clearly demonstrate the existence of a resonance, sharper as the temperature decreases, that shows up as an abrupt change between ferromagnetic and antiferromagnetic indirect anisotropic exchange interaction between localized spins. The origin of this spin-switching finite-quality-factor effect is discussed in detail remarking on its dependence on model parameters, i.e., light-matter coupling, exchange interaction between impurities, detuning and quality factor. For parameters corresponding to the case of a (Cd,Mn)Te quantum dot, the resonance shows up for Q around 70 and detuning around 10 meV. In addition, we show that, for such a quantum dot, and the best cavities actually available (quality factors better than 200) the exchange interaction is scarcely affected.

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G. Chiappe, E. Louis y E. V. Anda. 2006-02-06. Switching the sign of photon induced exchange interactions in semiconductor microcavities with finite quality factors. https://doi.org/10.1103/physrevb.74.155320

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