Strongly electron-correlated semimetal RuI$_3$ with a layered honeycomb structure

TL;DR

This paper reports the synthesis and characterization of a high-pressure polymorph of RuI$_3$, revealing its semimetallic behavior, layered honeycomb structure, and strong electron correlations, distinct from related insulating compounds.

Contribution

It introduces a new layered honeycomb polymorph of RuI$_3$ with semimetallic properties and highlights the role of I 5$p$ contributions and electron correlations.

Findings

RuI$_3$ exhibits semimetallic behavior unlike $eta$-RuCl$_3$

The material has a layered honeycomb structure

Strong electron correlations are present in RuI$_3$

Abstract

A polymorph of RuI$_3$ synthesized under high pressure was found to have a two-layered honeycomb structure. The resistivity of RuI$_3$ exhibits a semimetallic behavior, in contrast to insulating properties in $\alpha$-RuCl$_3$. In addition, Pauli paramagnetic behavior was observed in the temperature dependence of a magnetic susceptibility and a nuclear spin-lattice relaxation rate 1/$T_1$. The band structure calculations indicate that contribution of the I 5$p$ components to the low-energy $t_\mathrm{2g}$ bands effectively decreases Coulomb repulsion, leading to semimetallic properties. The physical properties also suggest strong electron correlations in RuI$_3$.