Strongly correlated electrons in the ferroelectric metal LiOsO3

Abstract

The metallic $\mathrm{LiOs}{\mathrm{O}}_{3}$ undergoes a transition to a polar phase below ${T}_{s}\ensuremath{\approx}140\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. This unusual property provides a unique opportunity to study the interaction between free electrons and electric dipoles. We report a suite of measurements of physical properties in $\mathrm{LiOs}{\mathrm{O}}_{3}$ as a function of temperature, including resistivity and magnetoresistance down to 0.16 K, thermoelectric power, high-precision magnetization, specific heat, and thermal conductivity on textured single-crystal samples. Enhancements from the electron contribution to the specific heat and the paramagnetic susceptibility indicate that electrons in $\mathrm{LiOs}{\mathrm{O}}_{3}$ are highly correlated. An anomalously large Kadowaki-Woods ratio also supports the argument of strongly correlated electrons in $\mathrm{LiOs}{\mathrm{O}}_{3}$. In the nonpolar phase above ${T}_{s}$, electrons are coupled strongly to the lattice vibrations, which leads to the resistivity saturation at high temperatures and eventually a crossover to the hopping conduction. The data of thermal conductivity and specific heat are consistent with an order-disorder transition at ${T}_{s}$. The analysis of critical behavior in the resistivity, specific heat, and the thermal conductivity provides useful information for understanding the electron-dipole interaction in $\mathrm{LiOs}{\mathrm{O}}_{3}$.