研究目的
Investigating the coherent spin dynamics of electrons in tunnel-coupled CdTe and (Cd,Mn)Te quantum wells and the short range proximity effect induced by exchange interaction.
研究成果
The coherent spin dynamics of electrons in tunnel-coupled double quantum well structures is determined by the electron wave function penetration into the narrow QW and the strength of exchange interaction between the electrons and manganese ions in the narrow QW. The presence of two electron g factor components is revealed, both of which depend on barrier thickness and temperature. The observed difference in g factors is associated with two different subensembles of electrons and is caused by the stronger interaction of the resident electrons with manganese ions due to the weaker spatial localization of their wave function in comparison with the electrons bound in excitons.
研究不足
The technique used does not allow the determination of the sign of the g factor. The study is limited to relatively weak magnetic fields of 0.5 or 1 T, where the field dependence of the effective g factor is very small.
1：Experimental Design and Method Selection:
Time-resolved pump-probe Kerr rotation technique is used to study the coherent carrier spin dynamics. The pulsed emission from a mode-locked Ti:sapphire laser is split into the pump and probe beams. The polarization of the pump is modulated between left and right circular helicity. The pump-induced spin coherence is detected through the Kerr rotation of the linearly polarized probe beam.
2：Sample Selection and Data Sources:
The studied QW structures were grown on (100)-oriented GaAs substrates by molecular-beam epitaxy. The heterostructures consist of two quantum wells of CdTe and Cd
3：984Mn016Te of 20- and 8-nm width, respectively, separated by a thin Cd88Mg12Te spacer of varying thickness. List of Experimental Equipment and Materials:
Mode-locked Ti:sapphire laser, photoelastic modulator, cryostat, spectrometer, charge-coupled-device detector.
4：Experimental Procedures and Operational Workflow:
The samples are placed in a cryostat allowing temperature variation from
5：6 up to 300 K and application of magnetic fields up to 6 T. The light wave vector is parallel to the sample growth axis. In the Voigt (Faraday) geometry, the magnetic field is applied perpendicular (parallel) to the growth axis. Data Analysis Methods:
The Kerr rotation signals are analyzed to extract Larmor precession frequencies, spin dephasing times, amplitudes, and initial phases corresponding to different spin ensembles.
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