Room-Temperature Electron Spin Generation by Femtosecond Laser Pulses in Colloidal CdS Quantum Dots

Materials

Haifang Tong²  Donghai Feng²  Xiao Li²  Li Deng²  Yuxin Leng¹  Tianqing Jia² 

[1] State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China; E-Mail:;State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China; E-Mails:

关键词: electron spin;    optical manipulation;    pump-probe;    quantum dots;   

DOI  :  10.3390/ma6104523

来源: mdpi

【 摘 要 】

We present an experimental investigation of optical spin orientation in colloidal CdS quantum dots (QDs) by a femtosecond laser pulse at room temperature. The spin carrier and its spin-generation process are clarified. Firstly, the observed spin signals of CdS QDs in time-resolved Faraday rotation measurements are shown to belong to electron carriers, by comparing the spin dephasing dynamics and Landé g factor between CdS QDs and bulk materials. Secondly, spin dynamics unaffected by the faster carrier recombination suggests that the spin-polarized electrons are not photoexcited but resident in the dots. Moreover, hole spins should dephase very fast compared with electron spins, otherwise the trion (two electrons with opposite spin orientations and one hole) recombination process will affect the resident electron spin signals. The electron spin is generated in a short time of which the excitation light is absorbed and the resident electron is excited to trion states, i.e., of pulse durations. Due to fast hole spin dephasing, trion recombination gives null spin signals, and the subsequent electron spin dynamics is controlled by its intrinsic mechanisms.

【 授权许可】

CC BY   
© 2013 by the authors; licensee MDPI, Basel, Switzerland.