Electron Spins In Semiconductors Research Articles

Ultrafast manipulation of electron spin coherence.

A technique is developed with the potential for coherent all-optical control over electron spins in semiconductors on femtosecond time scales. The experiments show that optical "tipping" pulses can enact substantial rotations of electron spins through a mechanism dependent on the optical Stark effect. These rotations were measured as changes in the amplitude of spin precession after optical excitation in a transverse magnetic field and approach pi/2 radians. A prototype sequence of two tipping pulses indicates that the rotation is reversible, a result that establishes the coherent nature of the tipping process.

All-optical magnetic resonance in semiconductors

A scheme is proposed wherein nuclear magnetic resonance (NMR) can be induced and monitored using only optical fields. In analogy to radio-frequency fields used in traditional NMR, circularly polarized light creates electron spins in semiconductors whose hyperfine coupling could tip nuclear moments. Time-resolved Faraday rotation experiments were performed in which the frequency of electron Larmor precession was used as a magnetometer of local magnetic fields experienced by electrons in n-type gallium arsenide. Electron spin excitation by a periodic optical pulse train appears not only to prepare a hyperpolarized nuclear moment but also to destroy it resonantly at magnetic fields proportional to the pulse frequency. This resonant behavior is in many ways supportive of a simple model of optically induced NMR, but a curious discrepancy between one of the observed frequencies and classic NMR values suggests that this phenomenon is more complex.

The Problem of Optical Orientation of Electron Spins in Semiconductors

The Problem of Optical Orientation of Electron Spins in Semiconductors

Проблема оптической ориентации электронных спинов в полупроводниках

Проблема оптической ориентации электронных спинов в полупроводниках

Orientation of Electron Spins in Semiconductors

Orientation of Electron Spins in Semiconductors

Optical spin orientation of non‐equilibrium electrons in GaAs and GaAsAlAs solid solution

AbstractThe results of optical orientation investigation of electron spins in semiconductors excited by circularly polarized light are reported. The occurrence of orientation is due to the presence of spin‐orbit splitting of the valence band. The effect has been investigated by measuring the degree q of circular polarization of the recombination radiation and has been observed in GaAs crystals and the solid solution GaAsAIAs. The dependencies of q on the wavelength of the exciting light have been obtained at 77 and 4.2° K. It has been found that in the case of GaAs crystal E increases and on the contrary, decreases in the solid solution, with temperature decreasing from 77 to 4.2 °K. Depolarization of radiation in an outer magnetic field has been investigated and the lifetimes T of nonequilibrium carriers and the times of spin relaxation τs, are determined. For the GaAs crystal τ (77 °K) = (1.4 ± 0.2) × × 10−10 s and τs (77 °K) = (2.8 ± 0.6) × 10−10 s is found. These values increase with decreasing temperature and at 4.2 °K become equal to (2.4 ± 0.3) × 10−10 s and (8.0 ± 1.5) × × 10−10 s, respectively. In the case of GaAs‐AIAs t and T, have been found with an accuracy determined by the magnitude of the g‐factor.

Ориентация электронных спинов в полупроводниках

Ориентация электронных спинов в полупроводниках