标题： 在钴砷化物（La，Ca）Co$_2$（As，P）$_2$中的平带驱动的巡游磁性 显示英文标题

标题： Flat band driven itinerant magnetism in the Co-pnictides (La,Ca)Co$_2$(As,P)$_2$

摘要： 平坦能带可以引起强烈的电子关联效应，这有助于稳定磁性和超导态。 在这里，我们进行角度分辨光电子能谱和密度泛函理论计算，以研究钴砷化物 CaCo$_2$As$_2$和 LaCo$_2$P$_2$的电子结构。 我们发现，虽然铁磁性 LaCo$_2$P$_2$的$k_z$费米拓扑结构明显是二维的，但反铁磁性 CaCo$_2$As$_2$发展出一个三维费米面，其垂直于 Co-As 平面的能带色散类似于$zig-zag$。 此外，磁性是由费米能级处具有$d_{xy}$和$d_{z^2}$轨道特征的平带的电子关联驱动的。 我们的结果将电子维度和磁序联系起来，并强调沿$c$方向的 As-As 和 P-P 键强度在理解过渡金属砷化物的电子能带结构和丰富的相图中的关键作用。 显示英文摘要

摘要： Flat bands can induce strong electron correlation effects that help stabilize both magnetic and superconducting states. Here, we carry out angle-resolved photoemission spectroscopy and density functional theory calculations to study the electronic structure of the Co-pnictides CaCo$_2$As$_2$ and LaCo$_2$P$_2$. We find that, while the $k_z$ Fermi topology of ferromagnetic LaCo$_2$P$_2$ is markedly 2-dimensional, antiferromagnetic CaCo$_2$As$_2$ develops a 3D Fermi surface described by a $zig-zag$-like band dispersion perpendicular to the Co-As plane. Furthermore, the magnetism is driven by the electronic correlations of the flat bands with $d_{xy}$ and $d_{z^2}$ orbital character at the Fermi level. Our results link the electronic dimensionality and the magnetic order, and emphasize the critical role of the As-As and P-P bond strength along the $c$-direction to understand the electronic band structure and the rich phase diagram of transition metal pnictides.