Magneto-spectroscopy of two-dimensional systems: Many-and few-body effects (original) (raw)
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Charged Magnetoexcitons in Two Dimensions: Isolated X? and Many-Electron Effects
physica status solidi (b), 2001
The states of charged magnetoexcitons in two-dimensional systems are considered. Exact optical selection rules for intra-and inter-band processes are discussed. The effect of excess electrons on internal transitions of negatively charged excitons X À in quantum wells is studied experimentally and theoretically. An experimentally observed blue-shift with excess electron density is explained in terms of collective excitations, magnetoplasmons bound to a valence band hole.
Editor's Choice Charged Magnetoexcitons in Two Dimensions: Isolated Xand Many-Electron Effects
2001
The states of charged magnetoexcitons in two-dimensional systems are considered. Exact optical selection rules for intra-and inter-band processes are discussed. The effect of excess electrons on internal transitions of negatively charged excitons X À in quantum wells is studied experimentally and theoretically. An experimentally observed blue-shift with excess electron density is explained in terms of collective excitations, magnetoplasmons bound to a valence band hole.
2001
Spin-singlet and spin-triplet internal transitions of quasi-two-dimensional, negatively charged magneto-excitons (X −) and their evolution with excess electron density have been studied in GaAs/AlGaAs quantum-wells by optically detected resonance (ODR) spectroscopy. In the dilute electron limit, due to magnetic translational invariance, the ODR spectra are dominated by bound-to-continuum bands in contrast to the superficially similar negativelycharged-donor system D − , which exhibits strictly bound-to-bound transitions. With increasing excess electron density in the wells in the magnetic field region corresponding to Landau level filling factors ν < 2 the X −-like transitions
Surface Science, 1992
We describe a novel magnetotunnelling spectroscopy technique for probing the complicated dispersion curves of hole states in the quantum well of p-type double barrier resonant tunnelling structures. Strong mixing between light and heavy hole states is observed. Some of the states clearly exhibit negative hole effective mass for motion in the plane of the quantum well. The results are contrasted with the simple case of resonant tunnelling of electrons in in-plane and tilted magnetic fields. For electron resonant tunnelling in tilted fields, we observe additional peaks in I(V). These are due to non-Landau level index-conserving transitions from the two-dimensional emitter accumulation layer to the quantum well.
Physical Review B, 2004
We theoretically investigate the properties of neutral and charged excitons and of the biexciton in vertically coupled quantum dots, as a function of the in-plane magnetic field B ʈ. The main effect of the field consists in the suppression of the bonding-antibonding splitting, and in the resulting enhancement of the interdot correlations. As a consequence, the excitons form with the additional carrier a bound or an unbound complex depending on the sign of the charging, whereas the biexciton undergoes a transition between different quantum states with increasing B ʈ. The discussed behaviors and transitions show up in the field dependence of experimentally accessible quantities, such as the charged-exciton and biexciton binding energies.
Physica E: Low-dimensional Systems and Nanostructures, 2000
We present a study of interacting, separately conÿned electron and hole layers that are photoexcited in undoped GaAs=AlAs mixed types I-II quantum wells. The low-temperature interband photoluminescence spectra and circularly polarized integrated intensity were studied as a function of a perpendicularly applied magnetic ÿeld (B67 T) and 2DEG density (n e68 × 10 11 cm −2 ). The observed rich structure of the lowest Landau index magnetoexcitons and the strong intensity oscillations at integral ÿlling factors are interpreted as due to cooperative 2DEG-2DHG transitions and, possibly, to the formation of weakly bound inter-layer excitons. ?
Many body effects and internal transitions of confined excitons in GaAs and CdTe quantum wells
Solid State Communications, 2003
Many body effects contribute significantly to the energy states of electron-hole pairs confined in quantum wells in the presence of excess electrons. We present results of optically detected resonance spectroscopy of the internal transitions of photo-excited electron-hole pairs in the presence of excess electrons for GaAs QWs and CdTe QWs. Compared to the case of isolated negatively charged excitons, excess electrons produce a large blue shift of the internal transitions in modulation-doped GaAs quantum wells (QWs) for filling factor , 2, and similar effects are found in CdTe QWs. For filling factor .2 no internal transitions are observed. These measurements demonstrate the strong effects of electron-electron correlations on the internal transitions of charged excitons in these quasi-2D systems and the importance of magnetic translation invariance. In the presence of excess electrons, the observed internal transitions are those of a magnetoplasmon bound to a mobile valence band hole.
Intra-magnetoexciton Transitions in Semiconductor Quantum Wells
2002
Highly sensitive optically detected resonance experiments have shown that magnetoexcitons in GaAs-(Ga,AI)As semiconductor quantum wells have discrete internal energy levels, with transition energies found in the far-infrared (terahertz) region. Here we are concerned with a theoretical study of the terahertz transitions of light-hole and heavy-hole confined magnetoexcitons in GaAs-(Ga,A1)As quantum wells, under a magnetic field applied in the growth direction of the semiconductor heterostructure. The various magnetoexciton states are obtained in the effective-mass approximation by expanding the corresponding exciton-envelope wave functions in terms of appropriate Gaussian functions. The electron and hole cyclotron resonances and intra-magnetoexciton transitions are theoretically studied by exciting the allowed electron, hole and internal magnetoexcitonic transitions with far-infrared radiation. Theoretical results are obtained for both the intra-magnetoexciton transition energies and oscillator strengths associated with excitations from Is -like to 2s, 2p±, and 3p± -like magnetoexciton states, and from 2pto 2s -like exciton states. Present results are in overall agreement with available optically detected resonance measurements and clarifies a number of queries in previous theoretical work.
Solid State Communications, 2000
Eigenstates of two-dimensional charged electron-hole complexes in magnetic fields are considered. The operator formalism that allows one to partially separate the center-of-mass motion from internal degrees of freedom is presented. The scheme using magnetic translations is developed for calculating in strong magnetic fields the eigenspectra of negatively charged excitons X Ϫ , a bound state of two electrons and one hole.