A ferroelectric-like structural transition in a metal

Although metals cannot be ferroelectric in the strict sense of the term, it has long been predicted that they can undergo structural transitions that share similarities with ferroelectricity. LiOsO 3 is now shown to be an experimental realization of such a ferroelectric-like metal. Metals cannot exhibit ferroelectricity because static internal electric fields are screened by conduction electrons 1 , but in 1965, Anderson and Blount predicted the possibility of a ferroelectric metal, in which a ferroelectric-like structural transition occurs in the metallic state 2 . Up to now, no clear example of such a material has been identified. Here we report on a centrosymmetric ( ) to non-centrosymmetric ( R 3 c ) transition in metallic LiOsO 3 that is structurally equivalent to the ferroelectric transition of LiNbO 3 (ref. 3 ). The transition involves a continuous shift in the mean position of Li + ions on cooling below 140 K. Its discovery realizes the scenario described in ref. 2 , and establishes a new class of materials whose properties may differ from those of normal metals.