A. S. Brichkin

Electrical spin injection in forward biased Schottky diodes based on InGaAs–GaAs quantum well heterostructures

The authors demonstrate efficient hole spin injection from a ferromagnetic metal (Ni) contact in a forward biased light emitting Schottky diode (LESD) fabricated on a GaAs based heterostructure with a quantum well (QW). The spin polarization of the injected holes was detected by measuring the circular polarization of the electroluminescence (EL) from the near surface InGaAs∕GaAs QW. An intermediate gold layer has been used in order to improve the spin injection efficiency. Over 40% degree of circular polarization of the EL has been observed at T=2K for the LESD structure with Au–Ni–Au Schottky contact.

Bistability and nonequilibrium transitions in the system of cavity polaritons under nanosecond-long resonant excitation

The polarization dependence of nonequilibrium transitions in a multistable cavity-polariton system is studied under a nanosecond long resonant optical excitation at the normal and magic angle incidences with various polarizations of the pump beam. The temporal correlations between the frequency, intensity, and optical polarization of the intra-cavity field, which all undergo sharp threshold-like changes due to the spin dependent interaction of cavity polaritons, are visualized. The observed dynamics cannot be reproduced within the conventional semi-classical model based on the Gross-Pitaevskii equations. To explain the observed phenomena, it is necessary to take into account the unpolarized exciton reservoir which brings on additional blueshift of bright excitons, equal in the

Mechanisms of manganese-assisted non-radiative recombination in Cd(Mn)Se/Zn(Mn)Se quantum dots

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Controlling magnetic moment and its fluctuations in individual semimagnetic quantum dots with different exchange interactions

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EFFECT OF Mn IONS ON SPIN RELAXATION AND LIFE-TIME OF e-h COMPLEXES IN CdSe/ZnSe/ZnMnSe QUANTUM DOTS

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Fine structure of electron‐hole complexes in single semimagnetic quantum dots

polarization components. This model explains the effect of polarization instability under both pulsed and continuous wave resonant excitation conditions, consistently with the spin ring pattern formation that has recently been observed under Gaussian shaped excitation.

Longitudinal and transverse fluctuations of magnetization of the excitonic magnetic polaron in a semimagnetic single quantum dot

Mechanisms of non-radiative recombination of electron-hole complexes in Cd(Mn)Se/Zn(Mn)Se quantum dots accompanied by interconfigurational excitations of Mn(2+) ions are analyzed within the framework of the single-electron model of deep 3d levels in semiconductors. In addition to the mechanisms caused by Coulomb and exchange interactions, which are related because of the Pauli principle, another mechanism due to sp-d mixing is considered. It is shown that the Coulomb mechanism reduces to long-range dipole-dipole energy transfer from photoexcited quantum dots to Mn(2+) ions. The recombination due to the Coulomb mechanism is allowed for any states of Mn(2+) ions and e-h complexes. In contrast, short-range exchange and sp-d recombinations are subject to spin selection rules, which are the result of strong lh-hh splitting of hole states in quantum dots. Estimates show that efficiency of the sp-d mechanism can considerably exceed that of the Coulomb mechanism. The phonon-assisted recombination and processes involving the upper excited states of Mn(2+) ions are studied. The increase in PL intensity of an ensemble of quantum dots in a magnetic field perpendicular to the sample growth plane observed earlier is analyzed as a possible manifestation of the spin-dependent recombination.

Auger recombination of excitons in semimagnetic quantum dot structure in a magnetic field

The influence of exchange interaction between exciton and magnetic impurity spins on magnetic moment and its fluctuations in semimagnetic quantum dots has been investigated with the use of individual dot magnetophotoluminescence technique. In quantum dots with strong exchange interaction, both the polarization of magnetic ions and magnetic fluctuations in a dot are highly influenced by the formation of exciton magnetic polaron. In contrast, in the quantum dots with weak interaction, the localized exciton acts as a perfect noninvasive probe: it allows one to analyze the quantum-dot magnetic moment and its fluctuations with negligibly small influence on the dot magnetization. Numerical values of exchange magnetic field and magnetic polaron energy are obtained and analyzed for both types of dots.

Effect of s p − d exchange interaction on excitonic states in CdSe ∕ ZnSe ∕ Zn 1 − x Mn x Se quantum dots

Photoluminescence measurements on individual CdSe/ZnSe/ZnMnSe quantum dots in a magnetic field up to 11 T both parallel and perpendicular to the sample growth plane at 1.6 K reveal a qualitative difference between samples with different strength of the sp-d exchange interaction controlled by means of varying the thickness of the nonmagnetic ZnSe layer. The observed difference is related with the dependence of the non-radiative Mn assisted recombination and the spin relaxation on magnetic field and the strength of the exchange interaction.

Effect of Coulomb interaction on exciton-polariton condensates in GaAs pillar microcavities

Photoluminescence spectra of CdSe/ZnSe/ZnMnSe semimagnetic quantum dots were studies in Faraday and Voigt geometries in the magnetic field up to 11 T at T=1.6 K. Incorporation of the nonmagnetic ZnSe layer between CdSe quantum dot layer and semimagnetic barriers reduced the strength of sp‐d exchange interaction and hence broadening of emission lines that obscures an observation of the fine structure of electron‐hole complexes. This allows one to identify exciton, biexciton and trion lines in the spectra of quantum dots and study their fine structure. An account of both sp‐d and electron‐hole exchange interactions are required in order to describe the Zeeman splitting and polarization behavior of the spectra.