Extreme high-density electron gas using band engineered complex oxide interfaces*

The study of interfaces between polar and non-polar complex oxides has seen unprecedented growth due to their unique ability to display interface-stabilized ground states including high-density two-dimensional electron gas (equivalent to 0.5 electron/u.c./interface). In this talk, we will present detailed thickness dependent structural and electronic transport study of the MBE-grown NdTiO$_{\mathrm{3}}$/SrTiO$_{\mathrm{3}}$ and SrTiO$_{\mathrm{3}}$/NdTiO$_{\mathrm{3}}$/SrTiO$_{\mathrm{3}}$ heterostructures. High-resolution x-ray diffraction, atomic force microscopy, reflection high-energy electron diffraction, scanning transmission electron microscopy and different spectroscopy techniques reveal nearly stoichiometric composition and abrupt interfaces. We will review the long-standing question on the origin of carriers at these interfaces and will present novel routes to achieve carrier density in excess of 0.5 electron/unit cell/interface using band engineered oxide interfaces.