Superconductivity in (Ba,K)SbO3

Nat Mater. 2022 Jun;21(6):627-633. doi: 10.1038/s41563-022-01203-7. Epub 2022 Feb 28.


(Ba,K)BiO3 constitute an interesting class of superconductors, where the remarkably high superconducting transition temperature Tc of 30 K arises in proximity to charge density wave order. However, the precise mechanism behind these phases remains unclear. Here, enabled by high-pressure synthesis, we report superconductivity in (Ba,K)SbO3 with a positive oxygen-metal charge transfer energy in contrast to (Ba,K)BiO3. The parent compound BaSbO3-δ shows a larger charge density wave gap compared to BaBiO3. As the charge density wave order is suppressed via potassium substitution up to 65%, superconductivity emerges, rising up to Tc = 15 K. This value is lower than the maximum Tc of (Ba,K)BiO3, but higher by more than a factor of two at comparable potassium concentrations. The discovery of an enhanced charge density wave gap and superconductivity in (Ba,K)SbO3 indicates that strong oxygen-metal covalency may be more essential than the sign of the charge transfer energy in the main-group perovskite superconductors.