标题： 压力和应变对 La$_3$Ni$_2$O$_7$ $\textit{ab initio}$ $GW$ 电子结构的影响 显示英文标题

标题： Pressure and strain effects on the $\textit{ab initio}$ $GW$ electronic structure of La$_3$Ni$_2$O$_7$

摘要： 最近在La$_3$Ni$_2$O$_7$中发现临界温度超过80 K的超导性表明镍酸盐中存在非常规的配对机制，类似于铜氧化物中的情况，这可能是由于电子关联效应。 我们采用从头计算的方法，在压力和外延应变的影响下，通过多体自能的$GW$近似计算了La$_3$Ni$_2$O$_7$的电子结构，并考虑了关联效应。 我们发现费米面由一个特征铜酸盐形状的片状结构$\beta$和一个镍酸盐特有的圆柱形结构$\alpha$组成，这两个结构都来自于 Ni$e_g$轨道，准粒子权重有不可忽略的下降，并表现出有效的1D特性。 这种拓扑结构是由Ni-3$d_{z^2}$空穴口袋$\gamma$（被关联作用抑制）和一个由关联作用以及压力/应变效应诱导产生的La-5$d_{x^2-y^2}$电子口袋之间微妙平衡的结果，而低能下该电子口袋的作用一直被忽视。 与铜氧化物不同，La$_3$Ni$_2$O$_7$的电子结构已经可以通过从头计算正确描述，并且与实验结果一致，无需引入Hubbard$U$调整参数或诉诸强关联物理。 显示英文摘要

摘要： The recent discovery of superconductivity in La$_3$Ni$_2$O$_7$ at a critical temperature above 80~K points to a non-conventional pairing mechanism in nickelates as in cuprates, possibly due to electronic correlations. We have calculated from first principles the electronic structure of La$_3$Ni$_2$O$_7$ under the effect of pressure and epitaxial strain including correlations by the $GW$ approximation to the many-body self-energy. We find that the Fermi surface is composed of a characteristic cuprate-shape sheet $\beta$ plus a nickelate-specific cylinder $\alpha$, both from Ni $e_g$ orbitals, with a non-negligible drop in the quasiparticle weight and an effective 1D character. This topology results from a delicate balance between the Ni-3$d_{z^2}$ hole pocket $\gamma$, which is suppressed by correlations, and an emerging La-5$d_{x^2-y^2}$ electron pocket induced by both correlation and pressure/strain effects and whose role at low energy has been neglected so far. Unlike cuprates, the electronic structure of La$_3$Ni$_2$O$_7$ is already correctly described from ab initio and in agreement with the experiment without the need to introduce Hubbard $U$ adjustable parameters or to invoke a strongly correlated physics.