报告人：Prof. Fanyao Qu (屈凡尧 教授)
Institute of Physics, University of Brasilia (巴西利亚大学物理系)
邀请人： 解士杰 教授
Transition metal dichalcogenide (TMDC) monolayersexhibit intriguing fundamental physics of strongly coupled spin and valley degrees of freedom for charge carriers. It is possible to selectively address and read out the valley index optically by helicity-resolved measurements. Hence the spin-locked valley degree-of-freedom has been proposed as classical and quantum information carriers. However, the use of valley excitonic states of TMDC monolayer to store and manipulate information is hampered by fast carrier recombination and short valley lifetime. We propose theoretically a scheme to overcome such an obstacle, by applying a tilted exchange field through magnetic proximity effect in monolayer MoS2 deposited on a ferromagnetic insulating substrate. While the in-plane component of the exchange field brightens the dark exciton by spin mixing, the out-of-plane field can effectively gate the emission with an ON/OFF ratio around 3000. Importantly, the brightening is valley selective, leading to nearly 100% valley/spin polarization at room temperature. The resulting strongly gateable dark-exciton emission with long lifetime and near unity valley polarization makes it convenient to manipulate the valley degree of freedom, which may serve as a novelparadigm for valleytronics and optoelectronics applications.
屈凡尧现任巴西利亚大学物理系教授，曾先后在曲阜师范大学物理系、南加州大学伯克利分校物理系、加拿大科学院、巴西乌伯兰迪亚联邦大学、意大利国际理论物理研究中心和德克萨斯大学奥斯汀分校任职或访学。研究兴趣包括：二维材料和范德瓦尔斯异质结的电子结构、光热、量子输运及拓扑性质，范德瓦尔斯异质结的自旋和多激子的谷动力学，量子信息和纳米器件模拟等。先后在Phys. Rev. Lett., Phys. Rev. B和Appl. Phys. Lett等主流物理期刊发表论文百余篇，参与《Quantum-dot Based Light-emitting Diodes》等4部专著的编纂，在国际大会做邀请报告19次，并组织国际会议2次。