2021 journal article

Flat-band-induced itinerant ferromagnetism in RbCo2Se2

Physical Review B.

By: J. Huang*, Z. Wang*, H. Pang*, H. Wu*, H. Cao*, S. Mo*, A. Rustagi n, A. Kemper n ...

co-author countries: China 🇨🇳 United States of America 🇺🇸
Source: ORCID
Added: April 13, 2021

$A$Co$_2$Se$_2$ ($A$=K,Rb,Cs) is a homologue of the iron-based superconductor, $A$Fe$_2$Se$_2$. From a comprehensive study of RbCo$_2$Se$_2$ via measurements of magnetization, transport, neutron diffraction, angle-resolved photoemission spectroscopy, and first-principle calculations, we identify a ferromagnetic order accompanied by an orbital-dependent spin-splitting of the electronic dispersions. Furthermore, we identify the ordered moment to be dominated by a $d_{x^2-y^2}$ flatband near the Fermi level, which exhibits the largest spin splitting across the ferromagnetic transition, suggesting an itinerant origin of the ferromagnetism. In the broader context of the iron-based superconductors, we find this $d_{x^2-y^2}$ flatband to be a common feature in the band structures of both iron-chalcogenides and iron-pnictides, accessible via heavy electron doping.