Enhanced Valley Polarization in WS2/LaMnO3 Heterostructure
Enhanced Valley Polarization in WS2/LaMnO3 Heterostructure
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WS 2 /LaMnO 3 异质结构中增强的谷极化
DOI：
10.1002/smll.202106029
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发表时间：
2022-03-01
期刊：
影响因子：
13.3
通讯作者：
Xu，Xiulai
中科院分区：
文献类型：
--
作者：
Dang，Jianchen;Yang，Mingwei;Xu，Xiulai
单层过渡金属二硫族化合物在山谷电子领域具有广泛的应用前景。然而，由于谷间散射，谷极化度通常不高。在4.2 K的非共振激发下，利用WS2/ lamno3薄膜异质结构，单层WS2的谷极化大大增强，高达80%，远高于在SiO2/Si衬底上单层WS2的谷极化15%。此外，极大增强的谷极化可以保持到约160 K的高温，谷极化率为53%。谷极化的温度依赖性与LaMnO3的热磁曲线密切相关，表明ws2与LaMnO3之间存在激子-磁子耦合。介绍了一个简单的模型来说明潜在的机制。由于自旋轨道耦合导致单层过渡金属二硫族化合物的导带分裂，在异质结构中观察到两个具有相反谷极化的层间激子，进一步证实了ws2和lamno3的耦合。研究结果为利用铁磁范德华工程控制过渡金属二硫族化合物的谷电子特性提供了一条途径，为实际谷电子应用铺平了道路。
Monolayer transition metal dichalcogenides have attracted great attention for potential applications in valleytronics. However, the valley polarization degree is usually not high because of the intervalley scattering. Here, a largely enhanced valley polarization up to 80% in monolayer WS2under nonresonant excitation at 4.2 K is demonstrated using WS2/LaMnO3thin film heterostructure, which is much higher than that for monolayer WS2on SiO2/Si substrate with a valley polarization of 15%. Furthermore, the greatly enhanced valley polarization can be maintained to a high temperature of about 160 K with a valley polarization of 53%. The temperature dependence of valley polarization is strongly correlated with the thermomagnetic curve of LaMnO3, indicating an exciton–magnon coupling between WS2and LaMnO3. A simple model is introduced to illustrate the underlying mechanisms. The coupling of WS2and LaMnO3is further confirmed with an observation of two interlayer excitons with opposite valley polarizations in the heterostructure, resulting from the spin‐orbit coupling induced splitting of the conduction bands in monolayer transition metal dichalcogenides. The results provide a pathway to control the valleytronic properties of transition metal dichalcogenides by means of ferromagnetic van der Waals engineering, paving a way to practical valleytronic applications.