Effects of a longitudinal magnetic field on spin injection and detection in InAs/GaAs quantum dot structures. 2012

J Beyer, and P H Wang, and I A Buyanova, and S Suraprapapich, and C W Tu, and W M Chen
Department of Physics, Chemistry and Biology, Linköping University, 58183 Linköping, Sweden. beyer@ifm.liu.se

Effects of a longitudinal magnetic field on optical spin injection and detection in InAs/GaAs quantum dot (QD) structures are investigated by optical orientation spectroscopy. An increase in the optical and spin polarization of the QDs is observed with increasing magnetic field in the range 0-2 T, and is attributed to suppression of exciton spin depolarization within the QDs that is promoted by the hyperfine interaction and anisotropic electron-hole exchange interaction. This leads to a corresponding enhancement in spin detection efficiency of the QDs by a factor of up to 2.5. At higher magnetic fields, when these spin depolarization processes are quenched, the electron spin polarization in anisotropic QD structures (such as double QDs that are preferably aligned along a specific crystallographic axis) still exhibits a rather strong field dependence under non-resonant excitation. In contrast, such a field dependence is practically absent in more 'isotropic' QD structures (e.g. single QDs). We attribute the observed effect to stronger electron spin relaxation in the spin injectors (i.e. wetting layer and GaAs barriers) of the lower-symmetry QD structures, which also explains the lower spin injection efficiency observed in these structures.

UI MeSH Term Description Entries
D007204 Indium A metallic element, atomic number 49, atomic weight 114.818, symbol In. It is named from its blue line in the spectrum.
D003198 Computer Simulation Computer-based representation of physical systems and phenomena such as chemical processes. Computational Modeling,Computational Modelling,Computer Models,In silico Modeling,In silico Models,In silico Simulation,Models, Computer,Computerized Models,Computer Model,Computer Simulations,Computerized Model,In silico Model,Model, Computer,Model, Computerized,Model, In silico,Modeling, Computational,Modeling, In silico,Modelling, Computational,Simulation, Computer,Simulation, In silico,Simulations, Computer
D004578 Electron Spin Resonance Spectroscopy A technique applicable to the wide variety of substances which exhibit paramagnetism because of the magnetic moments of unpaired electrons. The spectra are useful for detection and identification, for determination of electron structure, for study of interactions between molecules, and for measurement of nuclear spins and moments. (From McGraw-Hill Encyclopedia of Science and Technology, 7th edition) Electron nuclear double resonance (ENDOR) spectroscopy is a variant of the technique which can give enhanced resolution. Electron spin resonance analysis can now be used in vivo, including imaging applications such as MAGNETIC RESONANCE IMAGING. ENDOR,Electron Nuclear Double Resonance,Electron Paramagnetic Resonance,Paramagnetic Resonance,Electron Spin Resonance,Paramagnetic Resonance, Electron,Resonance, Electron Paramagnetic,Resonance, Electron Spin,Resonance, Paramagnetic
D005708 Gallium A rare, metallic element designated by the symbol, Ga, atomic number 31, and atomic weight 69.72.
D001152 Arsenicals Inorganic or organic compounds that contain arsenic. Arsenic Compounds,Compounds, Arsenic
D013113 Spin Labels Molecules which contain an atom or a group of atoms exhibiting an unpaired electron spin that can be detected by electron spin resonance spectroscopy and can be bonded to another molecule. (McGraw-Hill Dictionary of Chemical and Technical Terms, 4th ed) Spin Label,Label, Spin,Labels, Spin
D016880 Anisotropy A physical property showing different values in relation to the direction in or along which the measurement is made. The physical property may be with regard to thermal or electric conductivity or light refraction. In crystallography, it describes crystals whose index of refraction varies with the direction of the incident light. It is also called acolotropy and colotropy. The opposite of anisotropy is isotropy wherein the same values characterize the object when measured along axes in all directions. Anisotropies
D045663 Quantum Dots Nanometer sized fragments of semiconductor crystalline material which emit PHOTONS. The wavelength is based on the quantum confinement size of the dot. They can be embedded in MICROBEADS for high throughput ANALYTICAL CHEMISTRY TECHNIQUES. Nanocrystals, Semiconductor,Semiconductor Nanocrystals,Semiconductor Nanoparticles,Dot, Quantum,Dots, Quantum,Nanocrystal, Semiconductor,Nanoparticle, Semiconductor,Nanoparticles, Semiconductor,Quantum Dot,Semiconductor Nanocrystal,Semiconductor Nanoparticle
D060526 Magnetic Fields Areas of attractive or repulsive force surrounding MAGNETS. Magnetic Field,Field, Magnetic,Fields, Magnetic

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