Spin Relaxation Dynamics In CdTe Quantum Dots

with the size of electronic devices continues to shrink, quantum confinement effects become more and more obvious, seriously restricting the conventional charge-based semiconductor devices. Spin is a pure quantum mechanical effect of electron. Electron spin orientation constitutes a two-state quantum system; therefore electron spin can be used as the information carrier or qubits to realize the information storage, transmission and amplification. For example, you may store the digital information ("0" and "1" of the binary logic) in the electron spin as a new generation of logic devices. Compared with the traditional electronic devices based on charge, spintronic devices have the advantages of non-volatility, high data-processing speed, high integration density and low power consumption.Spintronic devices require that spin-polarized carriers transport efficiently from one side of the device to the other one without losing the information carried by the spins. However, de-coherence in solid-state quantum systems is pretty strong. It has emerged as the major challenge of spintronics that how to keep spin coherence time as long as possible and realize spin coherent manipulation as fast as possible. This paper mainly discusses the interaction mechanism between femtosecond laser pulses and spins in semiconductor quantum dots. The optical properties and ultrafast dynamic processes of CdTe semiconductor nanostructures with different sizes have been studied by the linear spectra and the cross-polarized heterodyne third-order nonlinear transient grating technique. By comparing the spin relaxation in quantum dots with different sizes, we find that exciton spin relaxation rates of CdTe quantum dots follow the size-dependent characteristic of R-4.