Kerr effect induced by exchange interaction of electrons separated by a tunnel barrier in a double quantum well

TL;DR

This paper presents a theoretical model explaining the Kerr effect induced by electron exchange in a double quantum well structure, supported by experimental data, and estimates the interwell electron exchange constant.

Contribution

The study develops a theoretical model of the spin Kerr effect considering interwell electron exchange, validated by experiments on CdTe quantum wells.

Findings

The model accurately describes experimental Kerr effect results.

Estimated interwell electron exchange constant as approximately 0.9×10^{-15} eV·cm^2.

Demonstrated electron exchange influences spin dynamics in coupled quantum wells.

Abstract

In a structure with two tunnel-coupled quantum wells of different widths, the spin dynamics resulting from resonant pulsed optical pumping of the narrow-well exciton includes the wide-well electron magnetization dynamics. Our analysis shows that the effect is driven by electron exchange between narrow-well excitons and spin-polarized electrons in the wide well. A theoretical model of the spin Kerr effect has been developed accounting for the interwell electron spin exchange. In the studied double-well structure with CdTe and Cd$_{0.98}$Mn$_{0.02}$Te quantum wells and a well-separating barrier thickness of 5 monolayers (1.6 nm), the model accurately describes the experimental results and allows us to estimate the interwell electron exchange constant as $\delta_{e} \approx 0.9\times10^{-15}~\textrm{eV}~\textrm{cm}^{2}$.