Role of spin-orbit coupling effects in rare-earth metallic tetra-borides : a first principle study

TL;DR

This study uses first-principle calculations to explore how spin-orbit coupling influences the electronic structure of rare-earth tetraborides, revealing specific orbital splitting effects and their impact on the density of states.

Contribution

It provides a detailed analysis of SOC effects on the electronic structure of rare-earth tetraborides using advanced DFT methods, highlighting orbital splitting phenomena.

Findings

SOC causes splitting of rare-earth p-orbital peaks into j=0.5 and j=1.5 states.

In LaB4, SOC leads to spin-split 4f orbitals at the Fermi level.

Density of states at the Fermi level remains largely unchanged for most materials.

Abstract

We have investigated the electronic structure of rare-earth tetraborides, $\textrm{RB}_{4}$, using first-principle electronic structure methods (DFT) implemented in Quantum Espresso (QE). In this article we have studied heather-to neglected strong spin-orbit coupling (SOC) effects present in these systems on the electronic structure of these system in the non-magnetic ground state. The calculations were done under GGA and GGA+SO approximations using ultrasoft pseudopotentials and fully relativistic ultrasoft pseudopotentials (for SOC case). Perdew-Burke-Ernzerhof generalized gradient approximation (PBE-GGA) exchange-correlation functionals within the linearized plane-wave (LAPW) method as implemented in QE were used. The projected density of states consists of 3 distinct spectral peaks well below the Fermi energy and separated from the continuum density of states around the Fermi energy. The discrete peaks arises due to rare-earth $s$-orbital, rare-earth $p$ + B $p$ and B $p$-orbitals while the continuum arises due to hybridized B $p$, rare-earth $d$ orbitals. Upon inclusion of SOC the peak arising due to rare-earth $p$-orbitals gets split into two peaks corresponding to $j=0.5$ and $j=1.5$ configurations. In case of $\textrm{LaB}_{4}$, in the presence of SOC, spin-split $4f$ orbitals contributes to density of states at the Fermi level while the density of states at the Fermi level largely remains unaffected for all other materials under consideration.