Robustness of spin polarization against temperature in multilayer structure: Triple quantum well

Abstract

We address the temperature influence on the precessional motion of electron spins under a transverse magnetic field, studied in GaAs/AlGaAs triple quantum wells, using pump-probe Kerr rotation. In the presence of an applied in-plane magnetic field, the TRKR measurements show the robustness of carrier's spin polarization against temperature, which can be easily traced in an extended range up to 250 K. By tuning the pump-probe wavelength to the exciton bound to a neutral donor transition, we observed a remarkably long-lasting spin coherence (with dephasing time T2*> 14 ns) limited by the spin hopping process and exchange interaction between the donor sites, as well as the ensemble spread of the g-factor. The temperature dependent spin dephasing time revealed a double linear dependence due to the different relaxation mechanisms active in respective temperature ranges. We observed that the increase in sample temperature from 5 K to 250 K leads to a strong T2* reduction by almost 98%/97% for the excitation wavelengths of 823/821 nm. Furthermore, we noticed that the temperature increase not only causes the reduction of spin lifetime, but can also lead to the variation of the electron g-factor. Additionally, the spin dynamics were studied through the dependencies on the applied magnetic field and optical pump power.