Pentagonal palladium diselenide (PdSe₂) stands out for its exceptional optoelectronic properties, including high carrier mobility, tunable bandgap, and anisotropic electronic and optical responses. Herein, we systematically investigate photocarrier dynamics in PdSe₂ ribbons using polarization-resolved optical pump–probe spectroscopy. In thin PdSe₂ ribbons with a semiconductor phase, the photocarrier dynamics are found to be dominated by intraband hot-carrier cooling, interband recombination, and the exciton effect, showing weak crystalline orientation dependences. Conversely, in thick semimetal-phase PdSe₂ ribbons, the photocarrier relaxations governed by the electron-optical/acoustic phonon scattering strongly depend on the sample orientation, albeit with a degradation in in-plane anisotropy following hot-carrier cooling. Furthermore, we analyze the correlations between photocarrier dynamics and anisotropic energy dispersions of electronic structures across a wide range in k space, as well as the contributions from the anisotropic electron–phonon couplings. Our study provides crucial insights for developing polarization-sensitive photoelectronic devices based on PdSe₂.

中文翻译：

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PdSe2 带中光载流子动力学的非凡偏振和厚度依赖性

五角二硒化钯 (PdSe ₂ ) 因其卓越的光电特性而脱颖而出，包括高载流子迁移率、可调带隙以及各向异性电子和光学响应。在此，我们使用偏振分辨光学泵浦探针光谱系统地研究了 PdSe ₂带中的光载流子动力学。在具有半导体相的薄PdSe ₂带中，发现光载流子动力学主要由带内热载流子冷却、带间复合和激子效应主导，表现出弱的晶体取向依赖性。相反，在厚的半金属相PdSe ₂带中，由电子光学/声声声子散射控制的光载流子弛豫强烈依赖于样品取向，尽管热载流子冷却后面内各向异性会降低。此外，我们分析了k空间中大范围内的光载流子动力学和电子结构的各向异性能量色散之间的相关性，以及各向异性电子声子耦合的贡献。我们的研究为开发基于 PdSe _{2 的}偏振敏感光电器件提供了重要的见解。