Interacting many-body systems in quantum wells: Evidence for exciton-trion-electron correlations

We report on the nonlinear optical dynamical properties of excitonic complexes in CdTe modulation-doped quantum wells, due to many-body interactions among excitons, trions and electrons. These were studied by time and spectrally resolved pump-probe experiments. The results reveal that the nonlinearities induced by trions differ from those induced by excitons, and in addition they are mutually correlated. We propose that the main source of these subtle differences comes from the Pauli exclusion-principle through phase-space filling and short-range fermion exchange.Comment: 5 pages, 4 figures. accepted for publications in Phys. Rev.

Trionic Optical Potential for Electrons in Semiconductors

Laser-induced optical potentials for atoms have led to remarkable advances in precision measurement, quantum information, and towards addressing fundamental questions in condensed matter physics. Here, we describe analogous optical potentials for electrons in quantum wells and wires that can be generated by optically driving the transition between a single electron and a three-body electron-exciton bound state, known as a trion. The existence of a bound trion state adds a term to the ac Stark shift of the material proportional to the light intensity at the position of the electron. According to our theoretical calculations, this shift can be large relative to the thermal equilibrium temperature of the electron, resulting in a relatively strong optical potential that could be used to trap, guide, and manipulate individual electrons within a semiconductor quantum well or wire. These potentials can be thought of as artificial nano-structures on the scale of 100 nm that can be spin-dependent and reconfigurable in real-time. Our results suggest the possibility of integrating ultrafast optics and gate voltages in new resolved-carrier semiconductor opto-electronic devices, with potential applications in fields such as nano-electronics, spintronics, and quantum information processingComment: Article and Supplemental Materials; This is a preprint of the original submission to Nature Physic

Oscillatory behaviour in the nonlinear emission of semiconductor microcavities

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Oscillatory behaviour in the nonlinear emission of semiconductor microcavities

We have observed marked oscillations in the time-resolved photoluminescence of a semiconductor microcavity under non-resonant excitation conditions. Hot excitons, created with an ultrashort light pulse, rapidly relax into polaritons in the cavity with a large in-plane momentum K. Shortly after illumination, above a certain excitation power, the polaritons accumulate into an energy trap at the bottom of the dispersion and the light emission, governed by final-state stimulated scattering, starts at K similar to 0 (0degrees with respect to the normal of the sample). The angular dependence of the photoluminescence at negative detunings reveals that the emission is rapidly transferred to K similar to 2 x 10(4) cm(-1) (similar to15degrees), close to the point of inflection of the lower polariton branch, giving rise to an annular emission. The oscillations arise from a macroscopic coherent population in the lower polariton branch

Nonlinear optical dynamics of excitons and trions

We investigate the nonlinear optical dynamics of excitons and trions in CdTe modulation-doped quantum wells by time and spectrally resolved pump-probe experiments. We find that the nonlinearities induced by excitons are different from those due to the presence of the trions. From a comparison between the exciton and trion behaviours, we show that, at low temperature, trions are formed from excitons in about 10 picoseconds and, as the temperature is increased, a thermal equilibrium is reached between exciton and trion populations within 5 picoseconds

Dynamics of charged excitons in GaAs quantum wells under high magnetic field

We report on time-resolved photoluminescence studies of charged and neutral excitons in a modulation doped GaAs quantum well under resonant excitation and high magnetic field. The radiative lifetime of the charged exciton is rather short, 60 ps at zero held, and is found to increase by a factor of similar to 2 up to 7 T. The short lifetimes suggest that, under magnetic field, the exciton bound in the trion is delocalized. (C) 1998 Elsevier Science B.V. All rights reserved

Many-Body Interaction Evidenced through Exciton-Trion-Electron Correlated Dynamics

Interactions among excitons, trions, and electrons are studied in CdTe modulation-doped quantum wells. These many-body interactions are investigated through the nonlinear dynamical properties in the excitonic complexes using time and spectrally resolved pump and probe techniques. This study is performed as a function of temperature and densities of excitons, trions, and electrons. The results reveal that the nonlinearities induced by trions differ from those induced by excitons and moreover they are mutually correlated. The correlated behavior of excitons and trions manifests itself by crossed trion-exciton effects. We propose that the main source of these correlations is due to the presence of electrons in the quantum well and that its physical origin is the Pauli exclusion-principle. We find that, at 5 K, trions are formed from excitons within 10 ps; at 20 K a thermal equilibrium is reached within 5 ps

Charged exciton dynamics in GaAs quantum wells

We study the dynamics of the charged and neutral excitons in a modulation-doped GaAs quantum well by time-resolved photoluminescence under a resonant excitation. The radiative lifetime of the charged exciton is found to be surprisingly short, 60 ps. This time is temperature independent between 2 and 10 K, and increases by a factor of 2 at 6 T. We discuss our findings in view of present theories of exciton radiative decay. [S0163-1829(98)03143-9]

Many-body interaction evidenced through exciton-trion-electron correlated dynamics

Interactions among excitons, trions, and electrons are studied in CdTe modulation-doped quantum wells. These many-body interactions are investigated through the nonlinear dynamical properties in the excitonic complexes using time and spectrally resolved pump and probe techniques. This study is performed as a function of temperature and densities of excitons, trions, and electrons. The results reveal that the nonlinearities induced by trions differ from those induced by excitons and moreover they are mutually correlated. The correlated behavior of excitons and trions manifests itself by crossed trion-exciton effects. We propose that the main source of these correlations is due to the presence of electrons in the quantum well and that its physical origin is the Pauli exclusion-principle. We find that, at 5 K, trions are formed from excitons within 10 ps; at 20 K a thermal equilibrium is reached within 5 ps