Optical control of electron spin coherence in CdTe/(Cd,Mg)Te quantum wells

TL;DR

This paper demonstrates optical methods to manipulate electron spin coherence in CdTe/(Cd,Mg)Te quantum wells using short laser pulses, combining experimental measurements with theoretical modeling.

Contribution

It provides a detailed experimental and theoretical analysis of how laser pulses control electron spin coherence in quantum wells, including the roles of pulse delay and polarization.

Findings

Laser pulses can coherently control electron spin dynamics.

Additive and non-additive effects are experimentally distinguished.

A two-level model accurately describes the optical excitation process.

Abstract

Optical control of the spin coherence of quantum well electrons by short laser pulses with circular or linear polarization is studied experimentally and theoretically. For that purpose the coherent electron spin dynamics in a n-doped CdTe/(Cd,Mg)Te quantum well structure was measured by time-resolved pump-probe Kerr rotation, using resonant excitation of the negatively charged exciton (trion) state. The amplitude and phase shifts of the electron spin beat signal in an external magnetic field, that are induced by laser control pulses, depend on the pump-control delay and polarization of the control relative to the pump pulse. Additive and non-additive contributions to pump-induced signal due to the control are isolated experimentally. These contributions can be well described in the framework of a two-level model for the optical excitation of the resident electron to the trion.