AI 中文总结
研究外延应变对双层镍酸盐La$_3$Ni$_2$O$_7$电子结构与磁关联的影响，发现应变可调控其自旋-电荷密度波序，大压缩应变会抑制超导。
AI 中文摘要
采用DFT+动力学平均场理论方法，研究电子-电子关联及晶体结构的外延应变对双层Ruddlesden-Popper型镍酸盐La$_3$Ni$_2$O$_7$（LNO）正常态电子结构、准粒子能带重整化、费米面及磁关联的影响。研究结果显示出显著的轨道选择型重整化，且Ni 3d带具有强非相干性，表明Ni x²-y²与3z²-r²态接近轨道选择型局域化。LNO的电子性质对平面内应变高度敏感：与未应变LNO相比，拉伸应变及约-2%的中等压缩应变均能显著增强磁关联；在约-4%的大压缩应变下，观测到以γ费米面片消失为特征的Lifshitz转变，该转变与成键Ni 3z²-r²轨道特征的近全占据浅平带相关，导致磁关联急剧下降，暗示超导被抑制。总体而言，研究结果支持LNO中由费米面嵌套驱动的自旋-电荷密度波条纹不稳定性，表明压力与应变均可有效调控（抑制或增强）自旋-电荷密度波序，引发增强的自旋涨落。
英文摘要
Using the DFT+dynamical mean-field theory method we study the effects of electron-electron correlations and epitaxial strain of the crystal structure on the normal-state electronic structure, quasiparticle band renormalizations, Fermi surface, and magnetic correlations of the bilayer Ruddlesden-Popper nickelate La$_3$Ni$_2$O$_7$ (LNO). Our results exhibit a remarkable orbital-selective renormalization and strong incoherence of the Ni $3d$ bands, pointing to the proximity of the Ni $x^2-y^2$ and $3z^2-r^2$ states to orbital-selective localization. The electronic properties of LNO show a high sensitivity to the in-plane strain. We note that both a tensile and a moderate compressive strain (up to about $-2$\%) yield a significant enhancement of magnetic correlations compared to the unstrained LNO. Under a large compressive strain of about $-4$\%, we observe a Lifshitz transition characterized by the disappearance of the $γ$ Fermi surface sheet, which is associated with a nearly fully occupied, shallow flat-band of the bonding Ni $3z^2-r^2$ orbital character. As a result, we observe a sharp decrease of magnetic correlations, implying suppression of superconductivity. Overall, our results support the picture of spin- and change-density-wave stripe instability driven by the Fermi surface nesting in LNO. Our results suggest that both pressure and strain can effectively tune (suppress or enhance) spin-change-density-wave ordering, giving rise to enhanced spin fluctuations.
Comments11 pages, 7 figures
