Band-filling and correlation controlling electronic properties and magnetism in K$_{x}$Fe$_{2-y}$Se$_{2}$: A slave boson study

TL;DR

This study uses a slave-boson approach to explore how band filling influences the electronic and magnetic phases of K$_{x}$Fe$_{2-y}$Se$_{2}$, revealing diverse states from paramagnetic metals to orbital-selective Mott phases.

Contribution

It provides a detailed theoretical analysis of the correlation and band filling effects on the magnetic and electronic properties of K$_{x}$Fe$_{2-y}$Se$_{2}$ using a multi-orbital slave-boson model.

Findings

At three-quarter filling, KFe$_{2}$Se$_{2}$ is a paramagnetic bad metal.

At two-third filling, the system exhibits striped antiferromagnetic metallic behavior.

At half filling, a N\'eel antiferromagnetic metal and orbital-selective Mott phase are observed.

Abstract

In this paper we investigate the electronic and magnetic properties of K$_{x}$Fe$_{2-y}$Se$_{2}$ materials at different band fillings utilizing the multi-orbital Kotliar-Ruckenstein's slave-boson mean field approach. We find that at three-quarter filling, corresponding to KFe$_{2}$Se$_{2}$, the ground state is a paramagnetic bad metal. Through band renormalization analysis and comparison with the angle-resolved photoemission spectra data, we identify that KFe$_{2}$Se$_{2}$ is also an intermediate correlated system, similar to iron-pnictide systems. At two-third filling, corresponding to the Fe$^{2+}$-based systems, the ground state is a striped antiferromagnetic (SAFM) metal with spin density wave gap partially opened near the Fermi level. In comparison, at half filling case, corresponding to the Fe$^{3+}$-based compounds, besides SAFM, a $N\acute{e}el$ antiferromagnetic metallic ground state without orbital ordering is observed in the intermediate correlation range, and an orbital selective Mott phase (OSMP) accompanied with an intermediate-spin to high-spin transition is also found. These results demonstrate that the band filling and correlation control the electronic state, Fermi surface topology and magnetism in K$_{x}$Fe$_{2-y}$Se$_{2}$.