Multipeak quasielastic light scattering and high-frequency electronic excitations in honeycomb Li$_2$RuO$_3$

We measured the temperature dependence of low-frequency Raman spectra in Li$_2$RuO$_3$, and observed multipeak quasielastic scattering in the Ru honeycomb polarizations below and above the magnetostructural transition temperature. We attribute this scattering to the fluctuations of the energy density in the spin system. High-frequency electronic light scattering was observed at 2150 $cm^{-1}$. Its intensity increased significantly below the transition temperature, confirming substantial modification of electronic structure due to removal of degeneracy in $t_{2g}$-manifold of Ru$^{4+}$ ions.