Superconductivity in spin-orbit coupled BaBi$_3$ formed by in situ reduction of bismuthate films

Abstract

Oxygen-scavenging at oxide heterointerfaces has emerged as a powerful route for stabilizing metastable phases that exhibit interesting phenomena, including high-mobility two-dimensional electron gases and high T$_{c}$ superconductivity. We investigate structural and chemical interactions at the heterointerface formed between Al or Eu and the charged-ordered insulator, BaBiO$_3$, leading to emergent superconductivity at 6 K. A combination of X-ray diffraction and electron microscopy measurements shows that oxygen scavenging by the Eu and Al adlayers leads to the formation of superconducting intermetallic BaBi$_3$ in nominal Eu/BaBiO$_3$ and Al/BaBiO$_3$ bilayers. Anisotropic magnetotransport measurements and current-voltage signatures of quasi two-dimensional superconductivity are observed. The mechanisms behind quasi-two-dimensional superconductivity and the role of disorder remain to be clarified. These findings highlight the potential for the use of in situ reduction of bismuthate heterostructures as a platform for stabilizing materials with exotic functional properties. Additionally, the strong spin-orbit coupling at the Bi sites may pave the way for the realization of high T$_{c}$ topological superconductivity.