压力诱导双层镍酸盐La3Ni2O7中电子与磁性关联的演化
Pressure-Driven Evolution of Electronic and Magnetic Correlations in Bilayer Nickelate La3Ni2O7
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中文总结 AI 辅助
本研究结合DFT、cRPA和DMFT揭示高压下La3Ni2O7的电子与磁性关联演化，发现轨道选择性演化及近藤屏蔽主导超交换导致Tc单调下降，为其超导相图提供微观解释。
中文摘要 AI 辅助
近期发现的高压下双层La3Ni2O7中的高温超导电性引发了广泛研究兴趣，但调控其压力依赖超导转变温度（Tc）的微观机制仍不明确。本研究结合密度泛函理论（DFT）、约束随机相位近似（cRPA）和动力学平均场理论（DMFT），探究高压下La3Ni2O7的电子与磁性关联。研究发现，静水压力可增强层间跃迁和裸超交换能标（4t²/U），同时通过降低相对关联强度（U/W）使系统向更巡游的状态演化；关键是，结果揭示了轨道选择性演化：Ni的dx²⁻y²态巡游性增强，而Ni的dz²轨道仍保持较强的局域特性。这种压力诱导的巡游性显著增强了两类轨道间的杂化，导致巡游dx²⁻y²电子对局域dz²矩的近藤类屏蔽作用大幅增强，作为配对媒介的有效磁交换耦合（Jeff）在高压区被抑制。研究表明，高压下Tc的单调下降由近藤屏蔽主导超交换相互作用所致，为La3Ni2O7的圆顶形超导相图提供了一致的微观解释。
英文摘要
The recent discovery of high-temperature superconductivity in pressurized bilayer La3Ni2O7 has sparked intense research interest, yet the microscopic mechanism governing its pressure-dependent superconducting transition temperature (Tc) remains elusive. In this work, we investigate the electronic and magnetic correlations of La3Ni2O7 under high pressure using a combination of density-functional theory (DFT), constrained random phase approximation (cRPA), and dynamical mean-field theory (DMFT). We find that while hydrostatic pressure enhances the interlayer hopping and the bare superexchange energy scale (4t2/U), it simultaneously drives the system toward a more itinerant regime by reducing the relative correlation strength (U/W). Crucially, our results reveal a distinct orbital-selective evolution: the Ni dx2-y2 states become increasingly itinerant, whereas the Ni dz2 orbitals retain a more localized character. This pressure-induced itinerancy significantly enhances the hybridization between the two, leading to a dramatic amplification of the Kondo-like screening of the local dz2 moments by the itinerant dx2-y2 electrons. Consequently, the effective magnetic exchange coupling (Jeff), which serves as the pairing glue, is suppressed in the high-pressure regime. Our findings suggest that the monotonic decrease of Tc at high pressures is driven by the dominance of Kondo screening over superexchange interactions, providing a coherent microscopic explanation for the dome-shaped superconducting phase diagram in La3Ni2O7.
