Yang Shuai, Yu Yilun, Sui Fengrui, Ge Rui, Jin Rong, Liu Beituo, Chen Ye, Qi Ruijuan, Yue Fangyu
Key Laboratory of Polar Materials and Devices (MOE), Department of Electronics, East China Normal University, Shanghai 200241, China.
Shanghai Center of Brain-inspired Intelligent Materials and Devices, East China Normal University, Shanghai 200241, China.
ACS Nano. 2024 Dec 10;18(49):33754-33764. doi: 10.1021/acsnano.4c15485. Epub 2024 Nov 28.
Exploring valley manipulatable layered semiconductors is highly significant for valleytronic devices. Here, we report the phonon chirality and resulting inter/intravalley scattering in valley polarized van der Waals (vdW) layered ReSe by linearly/circularly polarized Raman (L/CPR), transmission (L/CPT), and photoluminescence (L/CPL) spectroscopic techniques. L/CPR combined with scanning transmission electron microscopy determines the Re chains' direction and displays the existence of chiral phonons. The LPT discloses the energetic valley polarization between the Re chains and its perpendicular crystal axis directions. Intriguingly, the valley polarization strength depends on the layer thickness even in a micrometer scale and abnormaly increases with temperature increase. Further, CPT manifests the optical rotation in ReSe due to strong chiral phonon-photon coupling. More essentially, L/CPL unveils a strong exciton-like effect (Stokes shift) that can be interpreted from the inter/intravalley scattering related to the (chiral) phonon-carrier coupling. This investigation suggests a promising platform based on a low-symmetry vdW ReSe semiconductor for exploring valley physics and fabricating valley(opto)tronic nanodevices.
探索可谷操控的层状半导体对谷电子学器件具有重要意义。在此，我们通过线性/圆偏振拉曼光谱（L/CPR）、透射光谱（L/CPT）和光致发光光谱（L/CPL）技术，报道了谷极化范德华（vdW）层状ReSe₂中的声子手性以及由此产生的谷间/谷内散射。L/CPR与扫描透射电子显微镜相结合，确定了Re链的方向并显示了手性声子的存在。LPT揭示了Re链与其垂直晶轴方向之间的能量谷极化。有趣的是，即使在微米尺度下，谷极化强度也取决于层厚，并且会随着温度升高而异常增加。此外，CPT表明由于强手性声子-光子耦合，ReSe₂中存在光学旋转。更重要的是，L/CPL揭示了一种强激子样效应（斯托克斯位移），这可以从与（手性）声子-载流子耦合相关的谷间/谷内散射来解释。这项研究表明，基于低对称性vdW ReSe₂半导体的平台在探索谷物理和制造谷（光）电子纳米器件方面具有广阔前景。
