15 research outputs found
Electrical resistance associated with the scattering of optically oriented electrons in n-GaAs
In a bulk GaAs crystal, an unusual magnetoresistance effect, which takes
place when a spin-polarized current flows through the sample, was detected.
Under conditions of optical pumping of electron spins, an external magnetic
field directed along the electric current and perpendicular to the oriented
spins decreases the resistance of the material. The phenomenon is due to the
spin-dependent scattering of electrons by neutral donors. It was found that the
sign of the magnetoresistance does not depend on the sign of the exciting light
circular polarization, the effect is even with respect to the sign of the spin
polarization of the carriers, which indicates a correlation between the spins
of optically oriented free electrons and electrons localized on donors.Comment: 9 pages, 4 figure
Two-step model versus one-step model of the inter-polarization conversion and statistics of CdSe/ZnSe quantum dot elongations
The magneto-optical inter-polarization conversions by a layer of quantum dots
have been investigated. Various types of polarization response of the sample
were observed as a function of external magnetic field and of the orientation
of the sample. The full set of experimental dependences is analyzed in terms of
a one-step and a two-step model of spin evolution. The angular distribution of
the quantum dots over the directions of elongation in the plane of the sample
is taken into account in terms of the two models, and the model predictions are
compared with experimental observations
Linear polarization of the photoluminescence of quantum wells
The degree and orientation of the magnetic-field induced linear polarization
of the photoluminescence from a wide range of heterostructures containing
(Cd,Mn)Te quantum wells between (Cd,Mn,Mg)Te barriers has been studied as a
function of detection photon energy, applied magnetic field strength and
orientation in the quantum well plane. A theoretical description of this effect
in terms of an in-plane deformation acting on the valence band states is
presented and is verified by comparison with the experimental data. We
attempted to identify clues to the microscopic origin of the valence band spin
anisotropy and to the mechanisms which actually determine the linear
polarization of the PL in the quantum wells subject to the in-plane magnetic
field. The conclusions of the present paper apply in full measure to
non-magnetic QWs as well as ensembles of disk-like QDs with shape and/or strain
anisotropy.Comment: 21 pages, 10 figure
Features of spin dynamics of magnetic ions and charge carriers in self-organized quantum dots CdSe/ZnMnSe
Evidence of exchange interaction of localized carriers and transition metals in diluted II-VI nanostructures: ODMR study
Optically detected magnetic resonance study of (CdMn)Te/(CdMg)Te quantum wells allowed to reveal the formation of exchange-coupled complexes consisting of Mn ions and localized holes in quantum wells with excess hole concentration and the directional electron tunneling towards wider wells in multiple quantum well structures. The existence of a distribution of Mn-hole complexes that differ in a number of Mn ions interacting with a localized hole is justified. In colloidal cobalt doped ZnO nanocrystals, several nm in diameter, the interaction between the magnetic ions and the shallow donor electron in the confined system of ZnO quantum dots has been revealed. Direct evidence of interaction of Co ions with the interstitial Li shallow donor in the ZnO nanocrystal core and hyperfine coupling with 1H in the quantum dot shell have been demonstrated. (
Evidence of exchange interaction of localized carriers and transition metals in diluted II-VI nanostructures : ODMR study
Optically detected magnetic resonance study of (CdMn)Te/(CdMg)Te quantum wells allowed to reveal the formation of exchange-coupled complexes consisting of Mn ions and localized holes in quantum wells with excess hole concentration and the directional electron tunneling towards wider wells in multiple quantum well structures. The existence of a distribution of Mn-hole complexes that differ in a number of Mn ions interacting with a localized hole is justified. In colloidal cobalt doped ZnO nanocrystals, several nm in diameter, the interaction between the magnetic ions and the shallow donor electron in the confined system of ZnO quantum dots has been revealed. Direct evidence of interaction of Co ions with the interstitial Li shallow donor in the ZnO nanocrystal core and hyperfine coupling with 1H in the quantum dot shell have been demonstrated. (