NiO中具有增强轨道杂化的光稳定亚稳态电子态
Light-Stabilized Metastable Electronic State in NiO with Enhanced Orbital Hybridization
AI总结：
该研究发现NiO经光激发可产生具有增强轨道杂化的亚稳态，通过光谱与计算证实其形成非仅热驱动，提出光诱导屏蔽为调控关联氧化物的新机制，为光电材料设计提供新原则。
AI中文摘要：
光驱动调控关联金属氧化物的电子结构为优化光伏与光电化学技术所用材料提供了新机遇。我们表明，原型透明半导体和空穴传输材料NiO在跨电荷转移隙的光激发下会产生具有增强Ni 3d-O 2p轨道杂化的长寿命亚稳态。我们利用Ni K边X射线吸收光谱表征该态，该光谱可探测连续和脉冲紫外激发期间结构与电子变化对未占据p态密度的影响。在脉冲激发下，约10^20每立方厘米的高载流子密度会产生寿命约600皮秒的态，其中增强的杂化与晶格加热共存。相比之下，低得多的约10^13每立方厘米载流子密度下的连续紫外辐照可稳定类似的电子态，且晶格加热可忽略不计，表明其形成并非完全由热驱动。第一性原理DFT+U+V计算将光谱变化归因于更强的Ni 3d-O 2p杂化，该杂化改变了偶极允许的K边跃迁所探测的未占据Ni 4p态。我们将此变化归因于光激发后在位电子关联的动态屏蔽，这重新分布了电荷密度。由于轨道杂化决定了载流子传输和电荷转移能量学，我们的结果确定了光诱导屏蔽作为动态调控关联氧化物的一种机制，并为光电材料提出了新的设计原则。
英文摘要：
Light-driven control of electronic structure in correlated metal oxides offers new opportunities for optimizing materials used in photovoltaic and photoelectrochemical technologies. We show that photoexcitation of NiO, a prototypical transparent semiconductor and hole-transport material, across its charge-transfer gap produces a long-lived metastable state with enhanced Ni 3d-O 2p orbital hybridization. We characterize this state using Ni K-edge X-ray absorption spectroscopy, which probes how structural and electronic changes affect the unoccupied p density of states during continuous and pulsed ultraviolet excitation. Under pulsed excitation, high carrier densities of approximately 10^20 per cubic centimeter generate a state with a lifetime of approximately 600 picoseconds, in which enhanced hybridization coexists with lattice heating. By contrast, continuous ultraviolet irradiation at much lower carrier densities of approximately 10^13 per cubic centimeter stabilizes a similar electronic state with negligible lattice heating, demonstrating that its formation is not solely thermally driven. First-principles DFT+U+V calculations attribute the spectral changes to stronger Ni 3d-O 2p hybridization, which alters the unoccupied Ni 4p states probed by dipole-allowed K-edge transitions. We attribute this change to the dynamic screening of on-site electronic correlations following photoexcitation, which redistributes the charge density. Because orbital hybridization governs carrier transport and charge-transfer energetics, our results identify photoinduced screening as a mechanism for dynamically tuning correlated oxides and suggest new design principles for optoelectronic materials.
