Unique crystal field splitting and multiband RKKY interactions in Ni-doped EuRbFe4As4

Chenchao Xu,Chao Cao,Qijin Chen

doi:10.1038/s42005-019-0112-1

Chenchao Xu, Chao Cao + Show 1 more

Open Access

https://doi.org/10.1038/s42005-019-0112-1

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Abstract

The relationship between magnetism and superconductivity has been one of the most discussed topics in iron-based superconductors. Using first-principles calculations, we have studied the electronic structure of 1144-type iron-based superconductor EuRbFe4As4. We find the crystal field splitting of EuRbFe4As4 is unique, such that the d_{z^2} orbitals are closer to the Fermi level epsilon _{mathrm F} than the dxy orbitals. The Ruderman−Kittel−Kasuya−Yosida (RKKY) interaction strength is approximately 0.12 meV in pristine EuRbFe4As4. Upon Ni-doping on the Fe site, the RKKY interaction strength is barely changed upon Ni-doping due to the highly anisotropic Fermi surfaces and multiband effect, despite the drastically reduced dzx(y) density of state at epsilon _{mathrm F}. Finally, in both pristine and doped compounds, the RKKY interaction is primarily mediated through bands due to Fe-d_{z^2} orbitals. Our calculations suggest the RKKY interaction mediated by d_{z^2} orbital is probably responsible for the magnetism in EuRbFe4As4 and doesn’t change upon Ni-doping.

Highlights

The relationship between magnetism and superconductivity has been one of the most discussed topics in iron-based superconductors
The parent compounds of FeSCs are non-superconducting and undergo structural transition from tetragonal lattice to orthorhombic lattice followed by a spin density wave (SDW) transition when the temperature is decreased
Liu et al and Kawashima et al.[5,6] managed to make an intergrowth structure of RbFe2As2 and EuFe2As2 leading to another 1144-type compound EuRbFe4As4

Summary

Introduction

The relationship between magnetism and superconductivity has been one of the most discussed topics in iron-based superconductors. Using first-principles calculations, we have studied the electronic structure of 1144-type iron-based superconductor EuRbFe4As4. Upon Ni-doping on the Fe site, the RKKY interaction strength is barely changed upon Ni-doping due to the highly anisotropic Fermi surfaces and multiband effect, despite the drastically reduced dzx(y) density of state at εF. In both pristine and doped compounds, the RKKY interaction is primarily mediated through bands due to Fe-dz[2] orbitals. Our calculations suggest the RKKY interaction mediated by dz[2] orbital is probably responsible for the magnetism in EuRbFe4As4 and doesn’t change upon Ni-doping. We present a systematic first-principles study of

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Conclusion