Anomalous temperature dependence of the the spin-flip thermalization time between the dark and bright exciton states in silicon nanocrystals

Optical spin control in nanocrystalline magnetic nanoswitches

We investigate the optical properties of (Cd,Mn)Te quantum dots (QDs) by looking at the excitons as a function of the Mn impurities positions and their magnetic alignments. When doped with two Mn impurities, the Mn spins, aligned initially antiparallel in the ground state, have lower energy in the parallel configuration for the optically active spin-up exciton. Hence, the photoexcitation of the QD ground state with antiparallel Mn spins induces one of them to flip and they align parallel. This suggests that (Cd,Mn)Te QDs are suitable for spin-based operations handled by light.

Spin blockades to relaxation of hot multi-excitons in nanocrystals

The rates of elementary photophysical processes in nanocrystals, such as carrier cooling, multiexciton generation, Auger recombination etc., are determined by monitoring the transient occupation of the lowest exciton band. The underlying assumption is that hot carriers relax rapidly to their lowest quantum level. Using femtosecond transient absorption spectroscopy in CdSe/CdS nanodots we challenge this assumption. Results show, that in nanodots containing a preexisting cold exciton "spectator", \emph{only half of the photoexcited electrons}relax directly to the band-edge and the complementary …

Spin and energy transfer in nanocrystals without transport of charge

We describe a mechanism of spin transfer between individual quantum dots that does not require tunneling. Incident circularly-polarized photons create inter-band excitons with non-zero electron spin in the first quantum dot. When the quantum-dot pair is properly designed, this excitation can be transferred to the neighboring dot via the Coulomb interaction with either {\it conservation} or {\it flipping} of the electron spin. The second dot can radiate circularly-polarized photons at lower energy. Selection rules for spin transfer are determined by the resonant conditions and by the strong spi…

纳米晶体的光致发光线形：来自一阶和二阶振动耦合的贡献

Photoluminescence Line Shapes of Nanocrystals: Contributions from First- and Second-Order Vibronic Couplings

本文提出一种参数无关的方法，用于计算纳米晶体的光致发光光谱，揭示二次声子耦合对谱线宽的影响。

Spin--flip Limited Exciton Dephasing in CdSe/ZnS Colloidal Quantum Dots

The dephasing time of the lowest bright exciton in CdSe/ZnS wurtzite quantum dots is measured from 5 K to 170 K and compared with density dynamics within the exciton fine structure using a sensitive three-beam four-wave-mixing technique unaffected by spectral diffusion. Pure dephasing via acoustic phonons dominates the initial dynamics, followed by an exponential zero-phonon line dephasing of 109 ps at 5 K, much faster than the ~10 ns exciton radiative lifetime. The zero-phonon line dephasing is explained by phonon-assisted spin-flip from the lowest bright state to dark exciton states. This is…

玻璃基质中 CuCl 纳米晶内载流子的 Landé g 因子与自旋动力学

Landé g-factors and spin dynamics of charge carriers in CuCl nanocrystals in a glass matrix

该研究结合多种磁光光谱与六带价带理论，测量并建模玻璃基质中不同尺寸 CuCl 纳米晶的载流子 g 因子、激子跃迁及自旋动力学。