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Room temperature spin diffusion in (110) GaAs/AlGaAs quantum wells.

Hu C, Ye H, Wang G, Tian H, Wang W, Wang W, Liu B, Marie X - Nanoscale Res Lett (2011)

Bottom Line: Transient spin grating experiments are used to investigate the electron spin diffusion in intrinsic (110) GaAs/AlGaAs multiple quantum well at room temperature.The measured spin diffusion length of optically excited electrons is about 4 μm at low spin density.Increasing the carrier density yields both a decrease of the spin relaxation time and the spin diffusion coefficient Ds.

View Article: PubMed Central - HTML - PubMed

Affiliation: Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, P,O, Box 603, Beijing 100190, PR China. blliu@iphy.ac.cn.

ABSTRACT
Transient spin grating experiments are used to investigate the electron spin diffusion in intrinsic (110) GaAs/AlGaAs multiple quantum well at room temperature. The measured spin diffusion length of optically excited electrons is about 4 μm at low spin density. Increasing the carrier density yields both a decrease of the spin relaxation time and the spin diffusion coefficient Ds.

No MeSH data available.


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Schematic drawing of TSG setup and TSG signals. (a) kA and kB represent both the pump beams, kP is the probe beam, and kR is the reference beam. (b) TSG signal as a function of delay time at room temperature for two excitation powers: 2 and 18 mW.
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Figure 1: Schematic drawing of TSG setup and TSG signals. (a) kA and kB represent both the pump beams, kP is the probe beam, and kR is the reference beam. (b) TSG signal as a function of delay time at room temperature for two excitation powers: 2 and 18 mW.

Mentions: The investigated sample was grown on (110)-oriented semi-insulating GaAs substrate by molecular beam epitaxy. It consists of 20 planes of 8 nm thick GaAs QW with symmetric 27 nm Al0.28Ga0.72As barriers on both sides. The sample is nominally undoped. All the measurements are performed at RT. In the spin grating experiment, the laser pulses are generated by a mode-locked Ti:sapphire laser with 120 fs pulse duration and 76 MHz repetition frequency and split into primary pump and probe beams. The center wavelength is set to 830 nm to get the maximum signal of Kerr rotation through the standard time-resolved Kerr rotation technique [17]. Both pump and probe beams are focused on a phase mask with a period d. The phase mask splits each of the primary beams by diffraction into the m = ± 1 orders. The geometry of the spin grating experiment in the so-called box geometry is schematically presented in Figure 1a[18,19]. For orthogonal-linearly polarized pumps, the net polarization alternates between right and left circular polarization across the excitation spot while the total intensity of the incident light is uniform [9]. The period Λ of the TSG is simply: , where f1 and f2 are the focal lengths of two spherical mirrors. In our setup, the focal length of the first spherical mirror is fixed at f1 = 30.4 cm. The focal length f2 of the second spherical mirror can be changed to get a fine tuning of the period Λ. The spot sizes of both pump and probe beams are around 90 μm.


Room temperature spin diffusion in (110) GaAs/AlGaAs quantum wells.

Hu C, Ye H, Wang G, Tian H, Wang W, Wang W, Liu B, Marie X - Nanoscale Res Lett (2011)

Schematic drawing of TSG setup and TSG signals. (a) kA and kB represent both the pump beams, kP is the probe beam, and kR is the reference beam. (b) TSG signal as a function of delay time at room temperature for two excitation powers: 2 and 18 mW.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211199&req=5

Figure 1: Schematic drawing of TSG setup and TSG signals. (a) kA and kB represent both the pump beams, kP is the probe beam, and kR is the reference beam. (b) TSG signal as a function of delay time at room temperature for two excitation powers: 2 and 18 mW.
Mentions: The investigated sample was grown on (110)-oriented semi-insulating GaAs substrate by molecular beam epitaxy. It consists of 20 planes of 8 nm thick GaAs QW with symmetric 27 nm Al0.28Ga0.72As barriers on both sides. The sample is nominally undoped. All the measurements are performed at RT. In the spin grating experiment, the laser pulses are generated by a mode-locked Ti:sapphire laser with 120 fs pulse duration and 76 MHz repetition frequency and split into primary pump and probe beams. The center wavelength is set to 830 nm to get the maximum signal of Kerr rotation through the standard time-resolved Kerr rotation technique [17]. Both pump and probe beams are focused on a phase mask with a period d. The phase mask splits each of the primary beams by diffraction into the m = ± 1 orders. The geometry of the spin grating experiment in the so-called box geometry is schematically presented in Figure 1a[18,19]. For orthogonal-linearly polarized pumps, the net polarization alternates between right and left circular polarization across the excitation spot while the total intensity of the incident light is uniform [9]. The period Λ of the TSG is simply: , where f1 and f2 are the focal lengths of two spherical mirrors. In our setup, the focal length of the first spherical mirror is fixed at f1 = 30.4 cm. The focal length f2 of the second spherical mirror can be changed to get a fine tuning of the period Λ. The spot sizes of both pump and probe beams are around 90 μm.

Bottom Line: Transient spin grating experiments are used to investigate the electron spin diffusion in intrinsic (110) GaAs/AlGaAs multiple quantum well at room temperature.The measured spin diffusion length of optically excited electrons is about 4 μm at low spin density.Increasing the carrier density yields both a decrease of the spin relaxation time and the spin diffusion coefficient Ds.

View Article: PubMed Central - HTML - PubMed

Affiliation: Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, P,O, Box 603, Beijing 100190, PR China. blliu@iphy.ac.cn.

ABSTRACT
Transient spin grating experiments are used to investigate the electron spin diffusion in intrinsic (110) GaAs/AlGaAs multiple quantum well at room temperature. The measured spin diffusion length of optically excited electrons is about 4 μm at low spin density. Increasing the carrier density yields both a decrease of the spin relaxation time and the spin diffusion coefficient Ds.

No MeSH data available.


Related in: MedlinePlus