Pump-induced probe reflectivity change for cocircularly polarized pulse and countercircularly polarized pulse as a function of delay time at room temperature. Pump photon energy is tuned at 1.393 eV (a) and 1.425 eV (b), respectively, which are larger than the band gap energy, but less than spin-orbit split-off energy.
Time evolution of reflectivity changes in probe beam at 70 K. Pump photon energies are 1.425 eV (a), 1.494 eV (b), and 1.512 eV (c).
(a) The solid and dashed lines are calculated from cocircularly and countercircularly polarized pump and probe beams, respectively. The positive and negative peaks are at corresponding to the renormalized band gap energy and the original band gap energy, respectively. The arrows in the inset indicate the critical photon energy transforming from bleaching to absorption. (b) The calculated reflectivity changes at 70 K with carrier densities of (solid line), (dashed line), (dotted line), and (dashed dotted line) from cocircularly polarized pump and probe. The inset is the enlargement of the shading area.
Carrier density dependence of spin relaxation time constant with fixed pump photon energy of 1.425 eV at 70 K (triangle) and 1.393 eV at room temperature (square).
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