二维过渡金属硫族化合物/功能材料异质结界面激子态及自旋输运调控机理研究

Two dimensional transition metal dichalcogenides (TMDC) show great application potential in the field of valleytronics. So far, it has been shown that valley spin can be controlled via optical methods. However, using electrical means to control the property of the valley is an important prerequisite to real applications. The phenomenon of valley relaxation and scattering leads to low spin polarization rate. Unfortunately, there are very few reports on this issue. On the other hand, there are still many unsolved scientific problems on how to achieve high polarization under these conditions. This project focuses on design and preparation of high quality TMDC/functional material heterojunction samples to realize the spin injection and regulation by electrical methods. We will further explore the mechanism to improve their spintronic performances. The purpose of this project is to make use of functional substrates to selectively exert the effects of local electrical and magnetic field in the TMDC samples by electrical and optical means, and control the valley polarization characteristics induced by spin-orbit coupling. This project will reveal the promotion mechanism of surface, interface and plasmon modification on valley polarization, interfacial exciton excitation, valley scattering and carrier transport properties, etc. The feasible schemes for the valley electron polarization, suppression of the inter-valley relaxation and scattering will also be given. We explore the electron-hole pairs decay dynamic affected by the defects, interfacial stress and interlayer interaction. This study will make contributions to the application of 2D TMDC materials in the field of spintronic devices.

二维过渡金属硫族化合物（TMDC）在自旋电子学及谷电子器件领域展现出巨大应用潜力，目前已实现光对谷自旋的控制，而利用电学手段调控谷自由度是其走向器件化的重要前提，但目前相关报道还较少。另外，谷间弛豫、散射等现象导致谷自旋极化率过低，如何提高该特性还存在许多尚未解决的科学问题。本项目将对TMDC/功能材料异质结进行设计并制备高质量样品，实现对样品自旋电子的电学注入和调控，并对性能提升机制展开深入探索。本项目拟借助承载TMDC的功能性基底，通过电学和光学手段在TMDC样品内选择性施加近域电、磁场微扰，调节自旋-轨道耦合导致的能谷极化特性。揭示表面、界面和表面等离子体特性对谷极化、界面激子激发、谷间散射、载流子输运等特性的调控机理，给出提升谷极化率、抑制谷间驰豫与散射的可行方案，探索缺陷位、界面应力与层间相互作用对激子衰变过程的影响，为二维TMDC在自旋电子器件领域中的应用做出贡献。

二维半导体材料在自旋电子学及谷电子器件领域展现出巨大应用潜力，本项目研究了二维过渡金属化合物/功能材料异质结的设计和高质量样品制备，探究了对二维材料自旋电子的调控，并对性能提升机制展开深入探索。探索了表界面特性对电子自旋相互作用的调控机理，揭示了缺陷位、应力与层间堆垛对电子自旋交换能的影响，为二维TMDC在自旋电子器件领域中的应用做出贡献。该项目研究发现WSe2/PtBr3范德华异质结构的形成可以通过Pt-Se-Pt的额外超交换路径将体系居里温度（Tc）提高到~410 K。该路径的自旋交换相互作用高达~22 meV，优于大多数其它二维磁性材料系统。面外应力可进一步将Tc提高到约636 K。层间堆叠排列方式与层间磁耦合通紧密关联，这极大地促进了其在自旋电子学应用中的潜力。此外，本项目阐述了范德瓦尔斯异质结构中的强磁界面耦合对设计新型电子器件的重要意义，发现了二维SnO中的自旋轨道耦合可以通过EuBrO的磁近邻效应来激活能谷极化和劈裂，提出了基于SnO/EuBrO这种独特电子结构的新型自旋电子器件的设计原理。构建了Janus二维SnPbO2,由于其空间反演对称性的破缺，在价带顶处产生了较大的自旋劈裂(约为67 meV)，通过应变或空穴掺杂可以进一步增强该自旋劈裂。更重要的是，在价带顶处除了Rashba态之外没有其他电子态，这使得它非常适合实际应用。