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Optical spin polarization by coherent magnetoabsorption generation.

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Spin orientation in GaAsSb/GaAs quantum wells is maintained by magnetoabsorption, leading to spin polarization peaks. This occurs when spin-flip times exceed optical recombination times, confirmed by a 3.5 ns spin lifetime.

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Area of Science:

  • Semiconductor physics
  • Quantum optics
  • Materials science

Background:

  • GaAsSb/GaAs quantum wells (QWs) are crucial for optoelectronic devices.
  • Understanding spin dynamics in QWs is vital for spintronics.

Purpose of the Study:

  • Investigate spin orientation in GaAsSb/GaAs QWs.
  • Elucidate the role of magnetoabsorption in spin polarization.

Main Methods:

  • Magneto-photoluminescence measurements in high magnetic fields.
  • Theoretical modeling using rate equations for spin-split states.
  • Time-resolved measurements with circularly polarized excitation.

Main Results:

  • Observed spin-dependent intensity oscillations due to interband transitions.
  • Identified spin-resolved absorption resonances contributing to spin polarization.
  • Determined a spin lifetime of 3.5 ns, validating theoretical predictions.

Conclusions:

  • Magnetoabsorption plays a key role in sustaining spin coherence in these QWs.
  • Spin polarization is achieved when spin-flip times are longer than optical recombination times.
  • Experimental results confirm the theoretical framework for spin dynamics in GaAsSb/GaAs QWs.