Hole spin relaxation in neutral InGaAs quantum dots: Decay to dark states

Abstract

The authors report measurements of hole spin relaxation in neutral InGaAs quantum dots using polarization-dependent time-resolved photoluminescence experiments. The single-particle hole spin relaxation was isolated from other spin flip processes in the electron-hole system by detecting the initial transfer of population from optically active to dark states. The results indicate that electron-hole exchange interactions play a negligible role in the carrier spin kinetics, and are consistent with a mechanism of hole spin relaxation via phonon-mediated virtual scattering between confined quantum dot states.

Spin relaxation in zinc blende and wurtzite CdSe quantum dots

“…Although the exact nature of this spectral density is unclear, the larger level spacing in the wurtzite QDs may account for the slower observed exciton spin flip rate. The spin relaxation rates determined in this work can be compared to the results of previous studies [20][21][22][23][24]. However, the observed spin relaxation rate varies considerably depending on the temperature, the type of QDs (self-assembled or colloidal, charged or neutral), the type of carrier of interest (electron, hole, exciton), and external perturbation (external magnetic field, charging of QDs), making direct comparison between the studies difficult.…”

“…This is in contrast to other techniques that have been used for studying spin relaxation in QDs, for example, time-resolved Faraday rotation [19][20][21] and time-resolved photoluminescence with circularly polarized light [22][23][24][25]. In both techniques, spin orientation is optically created by circularly polarized photoexcitation of suitably oriented QDs and its subsequent relaxation is manifested as the decay of the signal.…”

Exciton spin decay in quantum dots: single and double phonon ssisted transitions

“…The case of exciton spin has been experimentally investigated [3] but only some decay channels have been examined theoretically. Three relevant phonon-assisted processes have been identified so far.…”

Spin relaxation in charge-tunable InP quantum dots

“…Following considerations are needed to clarify the role of dark excitons in spin dynamics of neutral QDs. 30 In addition to the spin relaxation of correlated e-h pair, spin flip of single-particle holes takes place during energy relaxation and leads to the formation of dark excitons ↑⇑ in neutral QDs. 31 Our previous study on the resonant spin orientation has clarified that the generation ratio between the bright and dark excitons is around 2:1 for the quasiresonant excitation at 1.771 eV.…”