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Exciton (X) and trion (T) Zeeman splitting as a function of electron concentration. (A–C) correspond to .
Source publication
Reflectivity and photoluminescence spectra from CdTe/CdMgTe modulation doped quantum well structures were studied. We have found that the value and the sign of the trion reflectivity line's Zeeman splitting depends on the electron concentration in the quantum well, whereas the value and sign of the exciton line splitting are absolutely equal for al...
Context in source publication
Context 1
... at high concentrations (Fig2b and Fig 2c) the sign of the trion Zeeman splitting becomes opposite to the exciton splitting and to the splitting of other lines. Figure 3 shows the dependences of the exciton and trion Zeeman slitting on magnetic field for the samples with different electron concentrations corresponding to Fig.1. One can see that at low concentrations the exciton and the trion splittings are the same, but with increase in electron concentration the exciton splitting is conserved but the trion splitting changes its value and even its sign. ...
Citations
Low-temperature photoluminescence from high-quality GaAs quantum wells,
asymmetrically doped with carbon, are investigated under high magnetic
fields (up to 20 T) directed along the [001] growth axis. At higher
fields, in the σ- polarized emission, we observe
two well-resolved lines which are attributed to the recombination of
neutral (X) and charged (X+) excitons. In contrast, only the
neutral exciton line is observed for the σ+
polarization. From the difference of the X line positions for the two
polarizations we determine the effective Zeeman splitting of neutral
excitons and then the g factor gh of confined holes. We find
that gh depends substantially on the well size and changes
the sign at moderate magnetic fields. To explain the experimental
results, the valence Landau levels are calculated using the Luttinger
model beyond the axial approximation. We demonstrate that mainly the
excited hole levels contribute to the excitonic state at higher magnetic
fields. Due to their light-hole character, resulting from the
valence-band mixing, the excited hole states have a sizable overlap with
the electron states confined far from the doped barrier. The calculated
values of gh are in an excellent quantitative agreement with
the experimental data.
We report a study of magnetic responses of neutral and charged excitons in quantum wells, which are very sensitive to the strong spin hybridization of holes. This effect can be used to engineer the spin character of excitonic complexes in two-dimensional systems tuned by the magnetic field strength. Conditions for spin flip for each kind of excitonic complex is detailed and the nature of the effect discussed. Differences in the effective Zeeman splitting between neutral and charged excitons are theoretically predicted and unambiguously confirmed experimentally. Circularly polarized resolved photoluminescence has been used to study these effects under applied magnetic fields. The intertwining of spin dynamics of excitons and trions is discussed.
