S. Glutsch

Coherent dynamics and dephasing of one-dimensional magnetoexcitons in GaAs

We study the ultrashort dynamics and the dephasing processes of one-dimensional Lorentzian and Fano magnetoexcitons in GaAs, using temporally and spectrally resolved four-wave mixing. The dephasing of the Lorentzian magnetoexcitons is determined by quasi-particle scattering, dominated by exciton – exciton scattering at low temperatures. In contrast, the dephasing time of the Fano magnetoexcitons is intrinsically limited by the Fano coupling to the continuum. Quantum interference is observed if Fano magnetoexcitons contribute to the four-wave mixing signal. This effect is absent in the case of purely Lorentzian dynamics. We show that Lorentzian and Fano magnetoexciton resonances are coupled by Coulomb correlation and discuss the consequences of this coupling.

QUANTUM BEATS IN SEMICONDUCTORS

In this paper we present a new method to calculate the Faraday rotation using the Jones calculus applicable to light pulses. This result is used to calculate the quantum beats in a magnetic semiconductor generated by pump-probe experiments in Faraday geometry. Considering a six level system and neglecting band dispersion as well as Coulomb interaction we find the Luttinger parameter of the valence band to be the only band parameter contributing to the quantum beat frequency.

Ultrafast spectroscopy of GaAs under a magnetic field: Coulomb correlated magnetoexcitons in the 3D to 1D transition

Abstract Using transient four-wave mixing spectroscopy, we study the ultrafast nonlinear optical response of magnetoexcitons in GaAs at 1.6 K. By spectrally and temporally resolving the coherent emission, we measure the magnetic field dependence of Coulomb interactions between magnetoexcitons. Contrary to experiments performed in quantum wells, these interactions persist for field strengths up to 10 T.