博士后郑海红同学在国际纳米权威期刊Nano Research上发表论文

课题组博士后郑海红同学在国际纳米权威期刊Nano Research上发表论文

       近日，课题组博士后郑海红同学在刘老师的指导下，以第一作者在国际纳米权威期刊《纳米研究》(Nano Research，影响因子10.269)上发表题为“Enhanced Valley Polarization in WSe₂/YIG Heterostructures via Interfacial Magnetic Exchange Effect”(界面磁交换效应增强WSe₂/YIG异质结构中的谷极化)的实验论文。

图：通过界面磁交换效应增强WSe2/YIG异质结构中的谷极化

      二维(2D)层状材料具有卓越的激子和谷自旋特性，在近年来引起了广泛关注。特别是，单层过渡金属硫属化物由于它们的空间反演对称性破缺和自旋轨道耦合而被确定为谷电子学研究的理想候选材料，导致两个简并但能量不等的能谷的形成。当圆偏振光激发这些2D材料时，自旋谷特性使得电子和空穴选择性地极化到不同能谷中，从而产生谷极化发光。然而，要实现谷电子学器件，关键是调控每个能谷中电子的数量，以实现高谷极化。目前，大多数控制谷极化的方法，如高磁场、低温、等离子体和电性掺杂，仍然不够。近年来，人们在通过构建2D材料与附加层和基底的异质结来调节2D材料的谷特性方面做出了相当大的努力。2D材料与磁性材料的组合因其能够通过磁性基底的近距效应在单层2D材料中产生界面磁交换场而备受关注，这为调控谷极化提供了一种新方法。然而，界面磁交换场调控谷分裂和谷极化增强的机制还需要进一步研究。

     在本研究中，我们利用湿法转移技术构建了一个WSe₂/YIG异质结构，并观察到单层WSe₂中谷极化的显著增强，高达63%。我们的结果表明，磁性基底对激子的谷极化和发射效率具有强烈的增强效应，这是由于磁近效应导致的。此外，WSe₂/YIG异质结构中带电激子的谷极化性能显著增强，高达42%，这表明磁性基底对谷极化增强具有重要影响。此外，通过改变外部磁场，我们研究了磁化方向对谷极化增强的影响(高达63%)。我们的工作为理解谷极化增强的机制提供了新的见解，并为单层2D材料中谷电子学的发展提供了有前景的方法。

论文链接：https://link.springer.com/article/10.1007/s12274-023-5865-x

Comments:

The study highlights the potential of exploiting valley degrees of freedom as information carriers in the field of valleytronics. The authors focus on monolayer transition metal dichalcogenides (TMDs) with broken space-inversion symmetry, which exhibit valley pseudospins and are considered excellent platforms for investigating valley electronics. However, the presence of intervalley scattering poses a limitation on achieving high degrees of valley polarization.

To address this issue, the researchers constructed WSe₂/YIG heterostructures and observed a remarkable enhancement in valley polarization compared to monolayer WSe₂ on SiO₂/Si substrates. The interfacial magnetic exchange effect on the YIG magnetic substrate played a crucial role in this improvement, resulting in a significant increase of up to 63% in valley polarization. This finding suggests that magnetic heterojunctions can offer a novel means of regulating valley polarization.

Furthermore, the WSe₂/YIG heterostructures exhibited multiple sharp exciton peaks, attributed to the strong magnetic proximity effect at the interface between the magnetic substrate and WSe₂. This effect not only enhanced exciton emission efficiency but also demonstrated the potential of magnetic heterojunctions in magneto-optoelectronics.

Another notable observation was the influence of an external magnetic field on the magnetic direction of the substrate, which further enhanced valley polarization. This result reinforces the notion that the magnetic proximity effect plays a significant role in governing valley polarization.

Overall, the study presents an exciting advancement in the field of valleytronics, showcasing the potential of magnetic heterojunctions for regulating valley polarization. The findings contribute to the development of valley electronics and highlight the promising application of these heterostructures in magneto-optoelectronics.