Analytical method for determining quantum well exciton properties in a magnetic field

Benoît Marie Joseph Deveaud, François Morier-Genoud, Barbara Pietka
American Physical Society, 2015
Journal paper

We develop an analytical approximate method for determining the Bohr radii of Wannier-Mott excitons in thin quantum wells under the influence of magnetic field perpendicular to the quantum well plane. Our hybrid variational-perturbative method allows us to obtain simple closed formulas for exciton binding energies and optical transition rates. We confirm the reliability of our method through exciton-polariton experiments realized in a GaAs/AlAs microcavity with an 8 nm In-x Ga1-xAs quantum well and magnetic field strengths as high as 14 T.

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Benoît Marie Joseph Deveaud, François Morier-Genoud, Barbara Pietka
American Physical Society, 2015
Journal paper

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https://infoscience.epfl.ch/record/208098?ln=en

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Resonant femtosecond emission from quantum well excitons: The role of Rayleigh scattering and luminescence

Benoît Marie Joseph Deveaud

We study the ultrafast properties of secondary radiation of semiconductor quantum wells under resonant excitation. We show that the exciton density dependence allows one to identify the origin of secondary radiation. At high exciton densities, the emission is due to incoherent luminescence with a rise time determined by exciton-exciton scattering. For low densities, when the distance between excitons is much larger than their diameter, the temporal shape is independent of density and rises quadratically, in excellent agreement with recent theories for resonant Rayleigh scattering.

1997

Femtosecond dynamics of secondary radiation formation from quantum well excitons

Benoît Marie Joseph Deveaud

The time-resolved secondary emission of resonantly created excitons in GaAs quantum wells is studied using femtosecond up-conversion spectroscopy. The behaviour of the rise and decay of the secondary emission and reflectivity in quantum welts is strongly dependent upon the disorder at the interfaces, the exciton density and the temperature. In the case of low densities and temperatures the emission is independent of the exciton density and rises quadratically in time, in excellent agreement with recent theory for Rayleigh scattering from two-dimensional excitons subjected to disorder. These rise times are compared directly with T-2 times measured by time-integrated four-wave mixing (FWM). The comparison of the dynamics displayed in time-resolved secondary radiation and time-integrated FWM provide a clear understanding of the coherence properties of QW excitons in the first few picoseconds after excitation. High-contrast oscillations that are due to quantum beats between the heavy- and light-hole Is-states are seen. The visibility decay at very low densities is long tau(HL) = 25 ps and is related to the action of potential fluctuations on the scattering of heavy-hole and light-hole excitons. (C) 1998 Elsevier Science B.V. All rights reserved.

1998

Resonant Rayleigh scattering on quantum well excitons: Theory and experiment

Benoît Marie Joseph Deveaud, Vincenzo Savona

Time-resolved up-conversion measurements of secondary emission from multiple quantum wells under resonant femtosecond excitation are reported for GaAs multiple quantum wells with qualitatively different interface disorder. The transient resonant Rayleigh scattering presents very peculiar features such as a long-lived signal and a nonmonotonic behaviour, which cannot be explained by a classical model. A microscopic model is proposed, where the quantum mechanical equation for the microscopic polarization is solved numerically assuming a random two-dimensional potential with spatial correlation, and a phenomenological dephasing time. The model succeeds in reproducing the shape of the transients. It is shown that, for typical parameters of GaAs quantum well excitons, quantum mechanical features are essential in the description of the scattered intensity. The observed features of the signal are interpreted in terms of polarization beatings due to the energy quantization of exciton levels lying within the same fluctuation site.

2000

Polariton

In physics, polaritons pəˈlærᵻtɒnz,_poʊ- are quasiparticles resulting from strong coupling of electromagnetic waves with an electric or magnetic dipole-carrying excitation. They are an expression of

Exciton

An exciton is a bound state of an electron and an electron hole which are attracted to each other by the electrostatic Coulomb force. It is an electrically neutral quasiparticle that exists in ins

Quantum well

A quantum well is a potential well with only discrete energy values. The classic model used to demonstrate a quantum well is to confine particles, which were initially free to move in three dimensio