Is Ba 3 In 2 O 6 a high- T c superconductor?

It has been suggested that Ba In O might be a high- superconductor. Experimental investigation of the properties of Ba In O was long inhibited by its instability in air. Recently epitaxial Ba In O with a protective capping layer was demonstrated, which finally allows its electronic characterization. The optical bandgap of Ba In O is determined to be 2.99 eV in-the (001) plane and 2.83 eV along the -axis direction by spectroscopic ellipsometry. First-principles calculations were carried out, yielding a result in good agreement with the experimental value. Various dopants were explored to induce (super-)conductivity in this otherwise insulating material. Neither - nor -site doping proved successful. The underlying reason is predominately the formation of oxygen interstitials as revealed by scanning transmission electron microscopy and first-principles calculations. Additional efforts to induce superconductivity were investigated, including surface alkali doping, optical pumping, and hydrogen reduction. To probe liquid-ion gating, Ba In O was successfully grown epitaxially on an epitaxial SrRuO bottom electrode. So far none of these efforts induced superconductivity in Ba In O leaving the answer to the initial question of whether Ba In O is a high- superconductor to be 'no' thus far.