paper

Flat band driven itinerant magnetism in the Co-pnictides CaCo $_{2}$ As $_{2}$ and LaCo $_{2}$ P $_{2}$

arXiv:2503.02728

Abstract

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 $z i g - z a g$ -like band dispersion perpendicular to the Co-As plane. Furthermore, the magnetism is driven by the electronic correlations of the flat bands with $d_{x y}$ 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.

Flat band driven itinerant magnetism in the Co-pnictides CaCo2​As2​ and LaCo2​P2​

Abstract

Flat band driven itinerant magnetism in the Co-pnictides CaCo $_{2}$ As $_{2}$ and LaCo $_{2}$ P $_{2}$