Effect of spin orbit coupling and Hubbard $U$ on the electronic structure of IrO$_2$

TL;DR

This study investigates how spin-orbit coupling and electron-electron interactions influence the electronic structure of IrO$_2$, revealing a robust J$_{ m eff}$ = 1/2 state and a phase transition driven by Hubbard $U$.

Contribution

It provides a detailed analysis of the interplay between SOC and Hubbard $U$ in IrO$_2$, highlighting the persistence of J$_{ m eff}$ states and the phase diagram for metal-insulator transition.

Findings

Ir t$_{2g}$ states retain J$_{ m eff}$ = 1/2 character at the Fermi level

A metal-insulator transition occurs with increasing $U$, coinciding with magnetic change

SOC reduces the critical $U$ for the phase transition

Abstract

We have studied in detail the electronic structure of IrO$_2$ including spin-orbit coupling (SOC) and electron-electron interaction, both within the GGA+U and GGA+DMFT approximations. Our calculations reveal that the Ir t$_{2g}$ states at the Fermi level largely retain the J$_{\rm eff}$ = $\frac{1}{2}$ character, suggesting that this complex spin-orbit entangled state may be robust even in metallic IrO$_2$. We have calculated the phase diagram for the ground state of IrO$_2$ as a function of $U$ and find a metal insulator transition that coincides with a magnetic phase change, where the effect of SOC is only to reduce the critical values of $U$ necessary for the transition. We also find that dynamic correlations, as given by the GGA+DMFT calculations, tend to suppress the spin-splitting, yielding a Pauli paramagnetic metal for moderate values of the Hubbard $U$. Our calculated optical spectra and photoemission spectra including SOC are in good agreement with experiment demonstrating the importance of SOC in IrO$_2$.