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Biomedical subjects

E L Ivchenko

Publications and source records attributed to E L Ivchenko.

6 recordsLinked to original sources
PubMed2002

Hidden in-plane anisotropy of interfaces in Zn(Mn)Se /BeTe quantum wells with a type-II band alignment.

Circularly and linearly polarized radiation due to spatially indirect optical transitions is studied in semimagnetic (Zn,Mn)Se/BeTe and nonmagnetic ZnSe/BeTe quantum-well structures with a type-II band alignment. Because of the giant in-plane anisotropy of the optical matrix elements related to a particular interface, complete spin orientation of photocarriers induced by magnetic fields leads not to purely circular but instead to elliptical polarization of the luminescence. From comparison between theory and experiment the parameter of optical anisotropy of a ZnSe/BeTe interface is evaluated. The developed theoretical approach can be applied for the large class of nanostructures revealing optical anisotropy.

Journal Article↗
PubMed2002

Spin-galvanic effect.

There is much recent interest in exploiting the spin of conduction electrons in semiconductor heterostructures together with their charge to realize new device concepts. Electrical currents are usually generated by electric or magnetic fields, or by gradients of, for example, carrier concentration or temperature. The electron spin in a spin-polarized electron gas can, in principle, also drive an electrical current, even at room temperature, if some general symmetry requirements are met. Here we demonstrate such a 'spin-galvanic' effect in semiconductor heterostructures, induced by a non-equilibrium, but uniform population of electron spins. The microscopic origin for this effect is that the two electronic sub-bands for spin-up and spin-down electrons are shifted in momentum space and, although the electron distribution in each sub-band is symmetric, there is an inherent asymmetry in the spin-flip scattering events between the two sub-bands. The resulting current flow has been detected by applying a magnetic field to rotate an optically oriented non-equilibrium spin polarization in the direction of the sample plane. In contrast to previous experiments, where spin-polarized currents were driven by electric fields in semiconductor, we have here the complementary situation where electron spins drive a current without the need of an external electric field.

Journal Article↗
PubMed2002

Spin-sensitive bleaching and monopolar spin orientation in quantum wells.

Spin-sensitive bleaching of the absorption of far-infrared radiation has been observed in p-type GaAs/AlGaAs quantum well structures. The absorption of circularly polarized radiation saturates at lower intensities than that of linearly polarized light due to monopolar spin orientation in the first heavy-hole subband. Spin relaxation times of holes in p-type material in the range of tens of ps were derived from the intensity dependence of the absorption.

Journal Article↗
PubMed2001

Conversion of spin into directed electric current in quantum wells.

A nonequilibrium population of spin-up and spin-down states in quantum well structures has been achieved applying circularly polarized radiation. The spin polarization results in a directed motion of free carriers in the plane of a quantum well perpendicular to the direction of light propagation. Because of the spin selection rules the direction of the current is determined by the helicity of the light and can be reversed by switching the helicity from right to left handed. A microscopic model is presented which describes the origin of the photon helicity driven current. The model suggests that the system behaves as a battery which generates a spin polarized current.

Journal Article↗