The concept of pseudospins in graphene was previously introduced in order to describe the electron motion near the high-symmetry point of the Brillouin zone. Many physical propertiesarerelatedtothepseudospins.Inthiswork,wepresenta mechanism of mediating the pseudospin interaction by circularly polarized photons. This interaction can switch the out-of-plane component of pseudospins and enable graphene to exhibit a ferromagnetic behavior. This mechanism allows us to build an analog quantum simulator of exchange interaction in terms of the optical cavity and graphene. We give the coupling coefficient between the pseudospins located on any two points and calculate the average of the pseudospin component by a generating functionaltechnique.Wepredicta newtype ofplasmon-polariton involving the exchange interaction.

Conduction electron spins interacting with magnetic impurity spins can lead to an indirect exchange interaction between magnetic impurities in nonmagnetic metals or semiconductors, namely, RKKY interaction. In general, this RKKY coupling is too weak to apply on devices. In this paper, we find that when a laser field of appropriate frequency irradiates the nanosystems, it can greatly strengthen the RKKY interaction. This is the so-called optical resonant RKKY interaction. We give the resonant frequencies for different size samples, and calculate the exchange integrals for these samples on the near-resonant conditions. This optical resonant RKKY coupling may be strong enough to guarantee its application on spintronic devices.Résumé : L'interaction des spins des électrons de conduction avec les spins d'impuretés magnétiques peut mener à une interaction d'échange indirect entre les impuretés magnétiques dans des métaux non magnétiques ou des semi-conducteurs, nommément l'interaction RKKY. En général, cette interaction RKKY est trop faible pour avoir des applications dans des dispositifs. Nous trouvons ici que l'illumination laser du nano-système à une fréquence appropriée peut fortement augmenter l'interaction RKKY. Cet effet s'appelle l'interaction RKKY en résonance optique. Nous donnons ici les fréquences de résonance pour différentes grosseurs d'échantillon et calculons les intégrales d'échange pour ces échantillons en situation près de la résonance. Ce couplage de RKKY en résonance optique peut être assez fort pour permettre son utilisation dans les dispositifs de spintronique. [Traduit par la Rédaction]

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We develop a quantum theory to deal with the coherent magnon excitation in monolayer magnetic nanodots induced by a circularly polarized light. In our theoretical model, the exchange interaction, the magnetic dipole interaction and the light-matter interaction are all taken into account and an effective dynamic equations governing the magnon excitation is derived by a continuum approximation. Our theoretical model shows that the helicity of light and the magnetic dipole interaction govern the magnon excitation and result in the occurrence of various patterns for the spin z-component distribution. We present a scheme to manipulate the single-mode magnon excitation by properly tuning the light frequency.