Is Ba3In2O6a high- Tc superconductor?

Abstract

It has been suggested that Ba₃In₂O₆might be a high-T_csuperconductor. Experimental investigation of the properties of Ba₃In₂O₆was long inhibited by its instability in air. Recently epitaxial Ba₃In₂O₆with a protective capping layer was demonstrated, which finally allows its electronic characterization. The optical bandgap of Ba₃In₂O₆is determined to be 2.99 eV in-the (001) plane and 2.83 eV along thec-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. NeitherA- norB-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, Ba₃In₂O₆was successfully grown epitaxially on an epitaxial SrRuO₃bottom electrode. So far none of these efforts induced superconductivity in Ba₃In₂O_6,leaving the answer to the initial question of whether Ba₃In₂O₆is a high-T_csuperconductor to be 'no' thus far.

Keywords: first-principles calculations; high-Tc superconductivity; molecular-beam epitaxy.