Zeeman splitting and g factor of heavy-hole excitons in InxGa1-xAs/GaAs quantum wells

Magneto-trions in a GaMnAs/Ga0.6Al0.4As Quantum Dot

Magneto bound exciton and the charged exciton in a GaMn 0.02 As / Ga 0.6 Al 0.4 As quantum dot are reported with the spatial confinement effect. The numerical calculations are carried out with the inclusion of exchange interaction between the carrier and the magnetic impurities. The binding energies of exciton and the trions and the optical transition energy are obtained as a function of dot radius. Numerical computations are followed using exact diagonalization method. The spin polaronic energy of the exciton and the charged excitons are obtained using a mean field theory in the presence of magnetic field strength. The magnetization of Mn ion impurities as a function of dot radius is investigated. The effective g-factor of conduction (valence) band electron (hole) is obtained in the GaMnAs quantum dot. The magnetic field induced size dependence of effective Landé g-factor is computed. The result shows that (i) the geometrical dependence on sp-d exchange interaction in the GaMn 0.02 As / Ga 0.6 Al 0.4 As quantum dot has great influence with the geometrical confinement, (ii) the monotonic behavior of effective g-factor with the reduction of dot radius is observed, (iii) the Landé factor is more sensitive if the geometrical confinement effect is included and (iv) the value of effective g-factor increases when the spatial confinement is enhanced for all the dot radii. Our results show that the effective Landé g-factor can be manipulated negative to positive values in the GaMn 0.02 As / Ga 0.4 Al 0.6 As quantum dot.

Spin polarization induced by in-plane electric and magnetic fields in two-dimensional heavy-hole systems

Using a nonequilibrium Green function approach, we systematically investigate the current induced spin polarization (CISP) in a two-dimensional heavy-hole system with cubic Rashba spin-orbit coupling, driven by in-plane electric and magnetic fields. We find that when a magnetic field is applied along the direction of electric field, the longitudinal conductivity drops monotonously with an increase of magnetic-field strength or of hole density. The spin polarization along the electric-field direction is just the Pauli paramagnetism and it quadratically increases with an increase of hole density. The nonvanishing out-of-plane component of spin polarization emerges for both short-range and long-range disorders, and it changes sign with the variation of magnetic field, especially for long-range hole-impurity scattering. In the magnetic-field dependences of this out-of-plane CISP and of the in-plane CISP perpendicular to the electric field, there are singular magnetic fields, below or above which the effects of magnetic field are completely different.

Anomalous circular polarization of photoluminescence spectra of individual CdSe nanocrystals in an applied magnetic field

We study the low-temperature magnetophotoluminescence from individual CdSe nanocrystals. Nanocrystals having a small "bright" exciton fine structure splitting (Delta_{XY}<0.5 meV) exhibit a conventional left and right circularly polarized Zeeman photoluminescence doublet in applied magnetic fields. In contrast, nanocrystals with large Delta_{XY} (>1 meV) show an anomalous magnetophotoluminescence polarization, wherein the lower-energy peak becomes circularly polarized with increasing field, while the higher-energy peak remains linearly polarized. This unusual behavior arises from strong mixing between the absorbing and emitting bright exciton levels due to strong anisotropic exchange interactions.