Pump-Probe Faraday Rotation and Ellipticity in an Ensemble of Singly Charged Quantum Dots

TL;DR

This paper develops a microscopic theory for spin Faraday rotation, Kerr rotation, and ellipticity signals in ensembles of singly charged quantum dots, showing how these techniques provide complementary insights into inhomogeneous QD ensembles.

Contribution

It introduces a comprehensive microscopic model for pump-probe Faraday and Kerr effects in quantum dot ensembles, including effects of pulse trains and spin coherence.

Findings

The theory aligns with phenomenological descriptions.

Signals depend on inhomogeneity and experimental setup.

Stationary electron spin polarization can be achieved with pulse trains.

Abstract

A description of spin Faraday rotation, Kerr rotation and ellipticity signals for single- and multi-layer ensembles of singly charged quantum dots (QDs) is developed. The microscopic theory considers both the single pump-pulse excitation and the effect of a train of such pulses, which in the case of long resident-electron spin coherence time leads to a stationary distribution of the electron spin polarization. The calculations performed for single-color and two-color pump-probe setups show that the three experimental techniques: Faraday rotation, Kerr rotation and ellipticity measurements provide complementary information about an inhomogeneous ensemble of QDs. The microscopic theory developed for a three-dimensional ensemble of QDs is shown to agree with the phenomenological description of these effects. The typical time-dependent traces of pump-probe Faraday rotation, Kerr rotation and ellipticity signals are calculated for various experimental conditions.