Optical spin pumping of modulation doped electrons probed by a two-color Kerr rotation technique

TL;DR

This study demonstrates optical spin pumping in modulation-doped CdTe quantum wells, revealing long spin relaxation times for localized electrons and shorter times for non-localized electrons using a two-color Kerr rotation technique.

Contribution

It introduces a two-color Hanle-MOKE method to distinguish spin relaxation times of localized and non-localized electrons in quantum wells.

Findings

Localized electrons have a spin relaxation time of 34 ns.

Non-localized electrons exhibit significantly shorter spin relaxation times.

Steady state spin density reaches about 10^8 cm^{-2}.

Abstract

We report on optical spin pumping of modulation electrons in CdTe-based quantum wells with low intrinsic electron density (by 10^10 cm^{-2}). Under continuous wave excitation, we reach a steady state accumulated spin density of about 10^8 cm^{-2}. Using a two-color Hanle-MOKE technique, we find a spin relaxation time of 34 ns for the localized electrons in the nearly unperturbed electron gas. Independent variation of the pump and probe energies demonstrates the presence of additional non-localized electrons in the quantum well, whose spin relaxation time is substantially shorter.