title: Effects of a longitudinal magnetic field on spin injection and detection in InAs/GaAs quantum dot structures.
abstract: 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.
authors.affiliation: Department of Physics, Chemistry and Biology, Linköping University, 58183 Linköping, Sweden. beyer@ifm.liu.se
authors.forename: J
authors.initials: J
authors.lastname: Beyer
authors.forename: P H
authors.initials: PH
authors.lastname: Wang
authors.forename: I A
authors.initials: IA
authors.lastname: Buyanova
authors.forename: S
authors.initials: S
authors.lastname: Suraprapapich
authors.forename: C W
authors.initials: CW
authors.lastname: Tu
authors.forename: W M
authors.initials: WM
authors.lastname: Chen
mesh_terms: D016880:Anisotropy; D001152:Arsenicals / Q000737:chemistry*; D003198:Computer Simulation; D004578:Electron Spin Resonance Spectroscopy; D005708:Gallium / Q000737:chemistry*; D007204:Indium / Q000737:chemistry*; D060526:Magnetic Fields; D045663:Quantum Dots; D013113:Spin Labels
chemical_list: D001152:Arsenicals; D013113:Spin Labels; D007204:Indium; C043055:gallium arsenide; D005708:Gallium; C076773:indium arsenide