AI 中文总结
该研究利用散焦工程电子能量损失光谱对多层CrSBr中激子色散进行动量分辨测量，结合第一性原理计算，发现其面内各向异性，将各向异性色散归因于长程电子 - 空穴交换相互作用，为研究低对称层状半导体中各向异性激子动力学提供了模型系统。
AI 中文摘要
我们报告了使用散焦工程电子能量损失光谱对多层CrSBr中激子色散进行的动量分辨测量，并得到了第一性原理计算的支持。观察到明显的面内各向异性，在$\lvert \boldsymbol{q} \rvert$ < 0.007 Å$^{-1}$范围内，激子沿$\Gamma$Y呈现线性色散，而沿$\Gamma$X几乎无色散。斜率达到7.02 eV Å，是低维系统中报道的最大斜率之一。计算重现了实验观察到的线性色散，证实了其内在起源。我们将各向异性色散归因于长程电子 - 空穴交换相互作用，这种相互作用因强面外限制而增强，并受跃迁偶极矩的方向选择规则支配。从顺磁到A型反铁磁态的磁相变的对比测量表明，色散基本不变，这表明激子传播与磁序之间的耦合可忽略不计。这些结果使CrSBr成为研究低对称层状半导体中各向异性激子动力学的模型系统。
英文摘要
We report momentum-resolved measurements of exciton dispersion in multilayer CrSBr using defocus-engineered electron energy-loss spectroscopy, supported by first-principles calculations. A pronounced in-plane anisotropy is observed, with the exciton exhibiting a linear dispersion along $Γ$Y within $\lvert \boldsymbol{q} \rvert$ < 0.007 Å$^{-1}$, while remaining nearly dispersionless along $Γ$X. The slope reaches 7.02 eV Å, among the largest reported in low-dimensional systems. The calculations reproduce the experimentally observed linear dispersion, confirming its intrinsic origin. We attribute the anisotropic dispersion to the long-range electron--hole exchange interaction, enhanced by strong out-of-plane confinement and governed by the directional selection rules of the transition dipole moment. Comparative measurements across the magnetic phase transition from the paramagnetic to the A-type antiferromagnetic state show that the dispersion remains essentially unchanged, indicating negligible coupling between exciton propagation and magnetic order. These results establish CrSBr as a model system for investigating anisotropic exciton dynamics in low-symmetry layered semiconductors.
Comments6 pages, 3 figures
