Discovery of Superconductivity in (Ba,K)SbO_3 [article]

Minu Kim, Graham M. McNally, Hun-Ho Kim, Mohamed Oudah, Alexandra Gibbs, Pascal Manuel, Robert Green, Tomohiro Takayama, Alexander Yaresko, Ulrich Wedig, Masahiko Isobe, Reinhard K. Kremer (+3 others)
2021 arXiv   pre-print
Superconducting bismuthates (Ba,K)BiO_3 (BKBO) constitute an interesting class of superconductors in that superconductivity with a remarkably high T_c of 30 K arises in proximity to charge density wave (CDW) order. Prior understanding on the driving mechanism of the CDW and superconductivity emphasizes the role of either bismuth (negative U model) or oxygen ions (ligand hole model). While holes in BKBO presumably reside on oxygen owing to their negative charge transfer energy, so far there has
more » ... een no other comparative material studied. Here, we introduce (Ba,K)SbO_3 (BKSO) in which the Sb 5s orbital energy is higher than that of the Bi 6s orbitals enabling tuning of the charge transfer energy from negative to slightly positive. The parent compound BaSbO_3-δ shows a larger CDW gap compared to the undoped bismuthate BaBiO_3. As the CDW order is suppressed via potassium substitution up to 65 T_c = 15 K. This value is lower than the maximum T_c of BKBO, but higher by more than a factor of two at comparable potassium concentrations. The discovery of an enhanced CDW gap and superconductivity in BKSO indicates that the sign of the charge transfer energy may not be crucial, but instead strong metal-oxygen covalency plays the essential role in constituting a CDW and high-T_c superconductivity in the main-group perovskite oxides.
arXiv:2107.06596v1 fatcat:cv3pn2i6wzgxfmzfvcp4lmnxfy