Potential superconducting interfaces in polar ABO3/Ba(Sr)BiO3 heterostructures

Abstract

We predict that interfacing the known superconducting oxide $\mathrm{Ba}(\mathrm{Sr}){\mathrm{BiO}}_{3}$ with a polar terminated perovskite oxide leads to a two-dimensional (2D) electron and/or hole gasses with a density similar to superconducting K-doped bismuthates. These interfaces have the potential for high-${T}_{\text{c}}$ superconductivity without the strong scattering present in randomly chemically substituted bismuthates. We present a detailed density functional theory (DFT) based study of the electronic structure of heterostructures involving polar 001 oriented ${\mathrm{LaLuO}}_{3}$ (LLO) and ${\mathrm{SrBiO}}_{3}$ (SBO) alternating layers. Beyond the thickness of four unit cells, 2D electron and hole gasses are formed at opposite interfaces of ${\mathrm{SrBiO}}_{3}$ with sheet charge densities on the order of ${10}^{14}\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{\ensuremath{-}2}$. The electron and hole gasses exist around the $Y$ ($X$) and $M$ points of the Brillouin zone, respectively. The separation of the gasses and therefore their interactions can be regulated by the SBO layer thickness. This provides a platform in which charge density waves, excitonic insulators or condensates, and superconductors compete for the ground state with the potential for new physical properties including high-${T}_{\text{c}}$ superconductivity.