Extraordinary quasi-two-dimensional magnetotransport properties of a LaAlO₃/SrTiO₃ heterostructure tailored with a surface TiO₂ atomic sheet

Epitaxial heterostructures of lanthanum aluminate (LaAlO₃) and strontium titanate (SrTiO₃) exhibit extraordinary quasi-two-dimensional magnetotransport properties at low temperatures. To elucidate the mechanisms responsible for the unique properties of these interfaces, which can guide the design of novel structures having high performances, extensive analyses of the magnetotransport properties at low temperatures are required. We report the magnetotransport properties of a LaAlO₃/SrTiO₃ system tailored with a topmost surface atomic sheet of titanium dioxide (TiO₂). Three unit cells of LaAlO₃ were deposited on a reconstructed SrTiO₃(001)-(13 × 13)-R33.7° substrate, yielding LaAlO₃ covered with a single-atom-thick TiO₂ sheet. The high-mobility electrons confined at the LaAlO₃/SrTiO₃ interface provided significantly high magnetoresistance ratios of +150% and -80% under magnetic fields perpendicular and parallel to the interface, respectively. The in-plane anisotropic magnetoresistance at 4.2 K reached approximately +30%, reflecting the Rashba spin-orbit interactions of the quasi-two-dimensional electrons. A high carrier concentration at the interface realized by the capping of LaAlO₃/SrTiO₃ with the surface TiO₂ sheet significantly contributed to the enhancement of magnetotransport properties arising from the Ti 3d orbitals.