Magnetic and electrical anisotropy with correlation and orbital effects in dimerized honeycomb ruthenate Li$_2$RuO$_3$

TL;DR

This study reveals significant magnetic and electrical anisotropy in Li$_2$RuO$_3$, linking it to correlation effects, orbital structure, and Ru-Ru dimerization, advancing understanding of its complex physical properties.

Contribution

The paper provides the first detailed experimental and theoretical analysis connecting anisotropic properties to orbital and correlation effects in dimerized honeycomb ruthenate Li$_2$RuO$_3$.

Findings

Resistivity along c* is greater than along b and a.

Magnetic susceptibility is highest along b-axis.

Anisotropy is explained by correlation effects and orbital structure.

Abstract

Li2RuO3 undergoes a structural transition at a relatively high temperature of 550 K with a distinct dimerization of Ru-Ru bonds on the otherwise isotropic honeycomb lattice. It exhibits a unique herringbone dimerization pattern with a largest ever reported value of the bond shrinkage of about ~ 0.5 \r{A}. Despite extensive studies, both theoretical and experimental, however, its origin and its effect on physical properties still remain to be understood. In this work, using high quality single crystals we investigated the anisotropy of resistivity ($\rho$) and magnetic susceptibility ($\chi$) to find a very clear anisotropy: $\rho$$_c*$ > $\rho$$_b$ > $\rho$$_a$ and $\chi$$_b$ > $\chi$$_a$ > $\chi$$_c*$. For possible theoretical interpretations, we carried out density functional calculations to conclude that these anisotropic behavior is due to the correlation effects combined with the unique orbital structure and the dimerization of Ru 4d bands.