Room-temperature spin coherence in zinc blende CdSe quantum dots studied by time-resolved Faraday ellipticity

The electron spin coherences in colloidal CdSe quantum dots with zinc blende structure are investigated by using ultrafast time-resolved Faraday ellipticity at room temperature. Particle size and magnetic field dependences of spin coherence indicate that the spin coherence is originated from the residual spin polarized electrons due to the exchange flip–flop scattering. The external magnetic field dependence of electron spin dephasing time suggests that the main limiting factor for the dephasing is the spread of electron spin Larmor precession frequency. In addition, the size dependence of electron g-factor in zinc blende CdSe quantum dots is determined to increase from 1.64 to 1.71 with decreasing diameters of quantum dots from 5.8 to 4.0 nm.