Institut des
NanoSciences de Paris
insp
insp
6.jpg

Soutenance de thèse de Guadalupe Arellano - Vendredi 29 novembre 2019 à 10 h

Guadalupe Arellano, doctorante dans l’équipe Photonique et cohérence de spin, soutient sa thèse le vendredi 29 novembre 2019 à 10 h.

INSP - Sorbonne Université - 4 place Jussieu - 75005 Paris - Barre 22-12, 4e étage, salle 426

Spin relaxation time of donors-bound electrons immersed in a semiconductor CdTe QW

JPEG

Abstract

We study the spin relaxation time of donor-bound electrons immersed in the middle of a CdTe quantum well (QW). By inserting the donors in a QW we increase the localization of the electron wave-function. In addition, the optical selection rules for circularly polarized light are purified, allowing a higher degree of optical orientation of the electron spins than in 3D crystals. A photo-induced Faraday rotation technique is used to measure the spin relaxation time of donor-bound electrons for different doping concentrations at low temperature in the insulating regime. In order to evaluate the spin relaxation mechanisms in our system, we calculate the exchange energy of a pair of donor-bound electrons immersed in the middle of an infinite QW, for any inter-donor distance and for different thicknesses. Then we explain the experimental behavior as an interplay of two mechanisms : hyperfine and anisotropic exchange interactions and we determine the CdTe spin-orbit constant : α_so = 0.079. We also develop an extended pump-probe experiment allowing to measure spin relaxation times at the microsecond scale. We briefly discuss the first experimental results for the longitudinal spin relaxation time of donor-bound electrons immersed in a CdTe QW with different doping concentrations. Finally, we investigate the temperature evolution of the spin relaxation in the range 10-80 K. The experimental behavior is explained by invoking spin exchange between electron spins localized on donors and the spin of electrons promoted to conduction states. While the spin of localized electrons undergoes the effect of hyperfine and anisotropic exchange interactions, the D’yakonov-Perel’ mechanism governs the spin relaxation of the conduction electrons.

Jury

  • Masha Vladimirova University of Montpellier
  • Pierre Gilliot LPCMS
  • Gabriel Hetet Laboratoire Pierre Aigrain
  • Emmanuelle Deleporte Laboratoire Aimé Cotton.