Possibility to realize spin-orbit-induced correlated physics in iridium fluorides

TL;DR

This study investigates iridium fluorides' crystal and electronic structures, revealing their potential for spin-orbit-induced correlated physics, with deviations from ideal models and implications for future quantum materials.

Contribution

It provides experimental and theoretical insights into iridium fluorides' electronic states, highlighting their deviation from idealized models and potential for novel correlated phenomena.

Findings

Consistent with Mott insulating scenario

Deviation of $j_{eff}=1/2$ state from SU(2) symmetry

Negligible magnetic ordering down to 20 K

Abstract

Recent theoretical predictions of "unprecedented proximity" of the electronic ground state of iridium fluorides to the SU(2) symmetric $j_{\mathrm{eff}}=1/2$ limit, relevant for superconductivity in iridates, motivated us to investigate their crystal and electronic structure. To this aim, we performed high-resolution x-ray powder diffraction, Ir L$_3$-edge resonant inelastic x-ray scattering, and quantum chemical calculations on Rb$_2$[IrF$_6$] and other iridium fluorides. Our results are consistent with the Mott insulating scenario predicted by Birol and Haule [Phys. Rev. Lett. 114, 096403 (2015)], but we observe a sizable deviation of the $j_{\mathrm{eff}}=1/2$ state from the SU(2) symmetric limit. Interactions beyond the first coordination shell of iridium are negligible, hence the iridium fluorides do not show any magnetic ordering down to at least 20 K. A larger spin-orbit coupling in iridium fluorides compared to oxides is ascribed to a reduction of the degree of covalency, with consequences on the possibility to realize spin-orbit-induced strongly correlated physics in iridium fluorides.