A strongly correlated polar metal LiOsO3*

LiOsO₃ is metallic and undergoes a second-order transition to a polar phase at T_c≈140 K. This unusual property provides a unique opportunity to study the interplay between itinerant electrons and electric dipoles. We report a suite of measurements of the properties of LiOsO₃ versus temperature, including resistivity and magnetoresisitance on a single crystal sample down to 0.16 K; Seebeck coefficient, Hall coefficient, high-precision magnetization, and the specific heat were made on polycrystalline samples. The results indicate that electrons become strongly correlated in responding to ferroelectric ordering of dipoles. We have monitored how the thermal conductivity is changed by dipole fluctuations at the transition and how it is influenced by ferroelectric domain boundaries at low temperatures to obtain information on interaction between the electrons and the dipoles. The observation of a transition from glassy to phonon-like thermal conductivity on cooling through T_c provides a solid proof that the ferroelectric transition is an order-disorder, not a displacive transition.