硕士生胡比奇同学在国际物理权威期刊Applied Physics Letters上发表论文

      近日，课题组成员胡比奇同学在刘老师的指导下，以第一作者在国际物理权威期刊《应用物理快报》(Applied Physics Letters上发表题为 “Engineering Polarization Anisotropy in WSe₂/CrOCl Heterostructures via Magnetic and Strain Effects”(WSe₂/CrOCl 异质结中极化各向异性的磁效应和应变调控)的实验论文。

图：WSe₂/CrOCl 异质结中极化各向异性的磁效应和应变调控

       二维 (2D)过渡金属二硫族化合物 (TMDCs)因其独特特性而备受关注，包括可调带隙、原子级厚度、高载流子迁移率、谷电子功能以及优异的机械柔性。这些特性使TMDCs成为新一代半导体器件，尤其在纳电子学和半导体技术˒领域具有广阔应用前景。在TMDC家族中，WSe₂作为典型材料，在光电探测器、场效应晶体管、电子器件及压电系统等方面展现出优异性能。然而，尽管TMDCs具有诸多优势，其单层材料本征的高晶格对称性导致其光学和电子响应主要呈各向同性，从而限制了其在需各向异性响应的技术领域中的应用。

近年来的研究表明，通过将TMDCs与具有不同对称性的材料堆叠形成范德华 (vdW)异质结，可打破其本征的各向同性，从而诱导出显著的各向异性光学现象。已有的研究体系包括WSe₂/BP、WSe₂/SiP、WS₂/BP和MoS₂/ReS₂等异质结，开启了对对称性破缺的探索，并拓展了TMDCs在光电子等领域的应用前景。此外，尽管已有部分关于TMDC/磁性材料异质结的优秀研究，如MoS₂/CrPS₄和MoS₂/CrOCl，丰富了对TMDCs在磁场中性能变化及其器件应用的理解，但目前尚缺乏关于磁性交互与应变联合调控TMDC光学特性的系统研究。为填补这一空白，亟需探索本征低对称性晶体结构的层状材料。CrOCl是一种稳定的范德华反铁磁体，具有正交晶格结构，展现出强烈的面内各向异性；同时，金纳米柱阵列提供了一种有效的应变调控手段，可实现对TMDCs异质结的精确力学变形和光电性能调制。

     在本研究中，我们采用干转移技术制备了WSe₂/CrOCl异质结构，并将其集成于Au纳米柱阵列之上，从而破坏了对称性并将WSe₂的各向同性行为转化为光学各向异性结构。角分辨和偏振分辨的光致发光 (PL)测量验证了该结构的光学各向异性特性。值得注意的是，WSe₂在Au纳米柱上也表现出各向异性光学响应，进一步表明应变是实现对称性破缺的另一机制。低温 (1.7 K)和磁场依赖测量结果显示，应变区域与平坦区域存在明显不同的各向异性行为，激子各向异性调制幅度可达约30%。磁场还可引起偏振角度旋转，最大可达90°，展现出可调的磁-光耦合效应。密度泛函理论计算表明，所观察到的各向异性源于WSe₂面内电荷分布的不均匀性，该效应由与CrOCl的界面耦合以及纳米柱阵列所引入的应变共同驱动，破坏了WSe₂本征的C₃对称性。本研究揭示了磁性效应、应变与光学各向异性之间的协同作用，为发展多功能偏振敏感光电子器件提供了新思路。

文章链接：https://pubs.aip.org/aip/apl/article/127/8/081902/3360515/Engineering-polarization-anisotropy-in-WSe₂-CrOCl

Comments:

This manuscript presents a compelling study on the interplay between magnetism, strain, and optical anisotropy in two-dimensional heterostructures composed of monolayer WSe₂, antiferromagnetic CrOCl, and Au nanopillar arrays. The authors effectively demonstrate that combining low-symmetry magnetic substrates and engineered strain fields can induce and modulate strong optical anisotropy in otherwise isotropic TMDCs. The use of polarization-resolved PL at both room and cryogenic temperatures provides solid experimental evidence of direction-dependent excitonic responses, with significant polarization contrast modulated by both magnetic fields and temperature. The reported magnetic-field-induced anisotropy modulation—up to ±30%—is particularly impressive and highlights the tunability of valleytronic features in these heterostructures.

Moreover, the integration of first-principles calculations provides an insightful mechanistic explanation rooted in in-plane charge redistribution due to interfacial coupling with CrOCl, supporting the experimental findings well.

Overall, the work is original and timely, offering a promising pathway for designing multifunctional 2D optoelectronic and spintronic devices. The only suggestion would be to further elaborate on the scalability and potential device integration of such heterostructures, as well as the reversibility and long-term stability of the anisotropic effects under cyclic magnetic/thermal stimuli. Nevertheless, the paper makes a valuable contribution to the field and will be of broad interest to researchers working on 2D materials, anisotropic optics, and magneto-optoelectronic systems.