磁性吸收光譜應用於磁鄰近效應誘發單層二硫化鉬能谷極化之研究

Valley spin-polarization in MoS2 single-layer induced via magnetic proximity effect: An approach of magnetic absorption spectroscopy

單層二硫化鉬在動量空間分裂出的自旋能谷為極其重要的量子特性，使二硫化鉬成為了繼石墨烯之後極具發展潛力的新穎二維材料，藉由磁鄰近效應誘發能谷極化的方法除了可做為量子編碼的方式，也將能谷電子學高度運用在記憶體科技。本篇研究中我們將提出一個方法去研究一個釔鐵石榴石與二硫化鉬交互偶合的系統中，如何產生磁鄰近效應與界面偶合的機制，藉由磁圓偏振二象性光譜技術，使釔鐵石榴石與二硫化鉬各自的磁性組態可以被解析。其中，可發現釔鐵石榴石與二硫化鉬之間的自旋轉移扮演決定性的關鍵角色，使二硫化鉬可以產生能谷極化且與釔鐵石榴石呈現反鐵磁性偶合，此外，這個系統也是目前報導出具有高於室溫磁鄰近效應的組合，為磁鄰近效應相關的能谷極化研究帶來嶄新的視野。

Single-layered transition-metal-dichalcogenides (TMDs), i.e. MoS2, are well known for their non-trivial valleytronic properties for such as valley-based memory or quantum computing. Exchange-coupling TMDs with ferromagnetic materials has been regarded as an important approach to manipulate the valley degree of freedom via the proximity effect, so the magnetism can serve to bridge the spin and valley in the single-layered TMDs. This work reports a study concerning how the proximity effect can be induced in a ferrimagnetic yttrium iron garnet (YIG)/MoS2 bilayer and be resolved by using a magnetic circular dichroism (MCD) spectroscopy. It reveals the proximity effect in the bilayer originates from a spin-transfer at the interface of YIG/MoS2, in which the minority spin of YIG would transfer to the conduction valley of MoS2 and make the spin-polarized valley antiferromagnetically coupled with YIG’s majority spins. The spin-transfer-associated proximity effect can be precisely resolved by using MCD technique. It provides an ideal research tool to study the proximity-related issues in the TMD-based exchange-coupled bilayer.