Ultrafast pump-probe dynamics in ZnSe-based semiconductor quantum-wells

TL;DR

This paper investigates ultrafast pump-probe dynamics in ZnSe quantum wells, combining experiments and theoretical modeling to understand excitonic resonance behavior and spin-flip processes on picosecond timescales.

Contribution

It provides a detailed comparison between experimental data and a semiconductor Bloch equation model, revealing spin-flip times and excitonic effects in ZnSe quantum wells.

Findings

Electron spin-flip occurs on a 30 ps timescale.

Energy renormalization and bleaching of excitonic resonances are characterized.

The model successfully explains experimental observations.

Abstract

Pump-probe experiments are used as a controllable way to investigate the properties of photoexcited semiconductors, in particular, the absorption saturation. We present an experiment-theory comparison for ZnSe quantum wells, investigating the energy renormalization and bleaching of the excitonic resonances. Experiments were performed with spin-selective excitation and above-bandgap pumping. The model, based on the semiconductor Bloch equations in the screened Hartree-Fock approximation, takes various scattering processes into account phenomenologically. Comparing numerical results with available experimental data, we explain the experimental results and find that the electron spin-flip occurs on a time scale of 30 ps.