AI 中文总结
本研究采用DFT+DMFT方法，揭示压力诱导UAs2发生轨道选择性电荷重分布（自掺杂），使费米面重构，为理解其高压超导提供电子结构依据，表明费米面嵌套与电荷涨落或提升超导Tc。
AI 中文摘要
近期在重费米子化合物UAs2中观测到压力诱导的超导现象，其临界温度Tc为铀基关联5f电子超导体中最高。为阐明该现象的微观起源，本研究采用密度泛函理论结合动力学平均场理论（DFT+DMFT）对其电子结构展开研究。常压下，计算重现了特征性近藤晶格电子结构，在Γ点和M点附近费米能处存在平坦杂化带，与角分辨光电子能谱（ARPES）结果吻合良好。施加压力后，研究发现电子从更局域的5f5/2轨道向更巡游的5f7/2轨道发生系统性转移，而U-5f轨道总占据数几乎保持不变。这种轨道选择性电荷重分布构成了压力诱导的自掺杂效应，使5f5/2电子从局域近藤态向电荷涨落增强的混合价态转变，引发低能电子结构的显著重构。值得注意的是，超导现象出现在费米面由两个分离的片状结构构成且嵌套效应增强的压力区间，当片状结构弯曲并合并为波纹状三维圆柱时，超导消失。本研究结果为理解UAs2的超导性提供了电子结构基础，表明费米面嵌套与电荷涨落可能对提高超导Tc有贡献，提示其与常规重费米子超导体存在潜在差异。
英文摘要
Superconductivity has recently been reported in the heavy-fermion compound UAs2 under pressure, with the highest Tc among uranium-based correlated 5f-electron superconductors. To elucidate its microscopic origin, we investigate its electronic structure using density functional theory combined with dynamical mean-field theory (DFT+DMFT). At ambient pressure, our calculations reproduce the characteristic Kondo-lattice electronic structure, with flat hybridization bands near the Fermi energy around the Γ and M points, in good agreement with angle-resolved photoemission spectroscopy (ARPES). Under pressure, we find a systematic transfer of electrons from the more localized 5f5/2 orbitals to the more itinerant 5f7/2 orbitals, while the total U-5f occupancy remains nearly unchanged. This orbital-selective charge redistribution constitutes a pressure-induced self-doping effect that drives the 5f5/2 electrons from a localized Kondo regime toward a mixed-valence regime with enhanced charge fluctuations, leading to a dramatic reconstruction of the low-energy electronic structure. Remarkably, superconductivity emerges in the pressure range where the Fermi surface consists of two disconnected sheets with enhanced nesting, but disappears when they bend and merge into a corrugated three-dimensional cylinder. Our results provide an electronic-structure basis for understanding superconductivity in UAs2 and suggest that Fermi-surface nesting and charge fluctuations may contribute to the enhanced superconducting Tc, pointing to a possible distinction from conventional heavy-fermion superconductors.
