Design and Synthesis of a Metallic Polar Aurivillius Oxide Bi2ReO6

The number of reported metallic compounds with polar crystal structures is limited due to the incompatibility of the acentricity and metallicity. Particularly, metallic oxides with polar crystal structures are rare. In this work, we designed a single-layer Aurivillius oxide Bi2ReO6 to explore metallic polar oxides. Single crystals and polycrystalline samples of Bi2ReO6 are synthesized by high-pressure methods. Bi2ReO6 crystallizes in the tetragonal structure with the polar space group P42cm (No. 101). Bi2ReO6 consists of alternative stacking of (Bi2O2)2+ layers and perovskite-like [ReO4]2– layers. Theoretical calculations further support that Bi2ReO6 with the polar space group is more stable and the tilts of ReO6 octahedra stabilize the system and break the inversion symmetry. Our magnetic and electrical data and low-temperature specific heat data indicate that Bi2ReO6 is a Pauli metal. The calculated electronic structures for Bi2ReO6 support the metallic nature, and the density of states at the Fermi level is contributed mainly from Re 5d orbitals hybridized with O 2p orbitals.