利用反鐵磁材料之磁鄰近效應誘發單層二硫化鉬能谷自旋極化之研究

Inducing valley spin-polarization of MoS2 single-layer via the antiferromagnetic proximity effect

單層過渡金屬二硫化合物(transition metal dichalcogenides，TMDs)在其六角形第一布里淵區之各個頂點上的能谷與自旋具有相依性而衍伸了特殊的能谷電子學，如何準確地控制能谷產生自旋極化，使其可以應用在能谷記憶體或量子技術為現今能谷電子學主要研究方向。本篇研究利用反鐵磁材料未補償面之磁鄰近效應誘發單層二硫化鉬能谷極化，並利用自旋解析光致發光光譜對二硫化鉬進行觀察，其中自旋極化激子的有無可用作判定極化成功與否；研究結果顯示，利用反鐵磁未補償面之局部鐵磁序可以成功誘發二硫化鉬產生顯著的能谷自旋極化現象，其磁鄰近效應之轉換溫度約在100 K以上，於相關文獻中屬於相對溫度較高的系統。本篇研究揭示了交換偶合凡德瓦異質材料領域中，反鐵磁材料可能賦予的嶄新視野和可期性。

Single layered transition-metal-dichalcogenides (TMD) are prominent for their coupled spin valleys at the hexagonal corners in the first Brillouin zone. Precisely control over the valley spin polarization has been regarded as an important approach to realize the valley-based memory or quantum technology. This work reports an effective control of using an antiferromagnet with an uncompensated surface to trigger a proximity effect in a single layered MoS2. The proximity effect is reflected on the spin-polarized excitons in the MoS2 and can be resolved by using a spin-resolved photoluminescence spectroscopy. The results reveal the importance of controlling the local ferromagnetic order in an antiferromagnet to trigger the interfacial exchange with MoS2, hence, leading to the significant spin-polarized valley. The transition temperature of the proximity effect was also found above 100 K, which is a relatively high marker among the associated literature. It reveals the antiferromagnet may be able to open a new horizon for the research field of exchange-coupled van der Waal’s heterostructure.