Assessing Broken Inversion Symmetry in Conductive Materials

The coexistence of broken inversion symmetry and metallic conductivity represents a pathway to novel physics and useful properties, but the mechanisms which unite these properties remain largely unexplored. The recent discovery and synthesis of LiOsO₃ [Shi et al., Nat. Mater. 12 (11) 1024-1027 (2013)] provides an opportunity to study noncentrosymmetric conductors in greater detail. Here we compare the lattice dynamical properties of the polar metal LiOsO₃ with the degenerately doped ferroelectric BaTiO₃ . We use density functional theory to investigate the interatomic force constants of both materials, providing insight into the driving forces behind the inversion symmetry-breaking structural transition. This information is coupled with the electronic and phononic structure to understand changes in off-centering driven by doping as opposed to intrinsic metallicity.