Insulator-to-metal transition at oxide interfaces induced by WO3 overlayers

Interfaces between complex oxides constitute a unique playground for two-dimensional electron systems (2DESs), where superconductivity and magnetism can arise from combinations of bulk insulators. The 2DES at the LaAlO3/SrTiO3interface is one of the most studied in this regard, and its origin is determined by the polar field in LaAlO3as well as by the presence of point defects, like oxygen vacancies and intermixed cations. These defects usually reside in the conduction channel and are responsible for a decrease of the electronic mobility. In this work, we use an amorphous WO3overlayer to obtain a high-mobility 2DES in WO3/LaAlO3/SrTiO3heterostructures. The studied system shows a sharp insulator-to-metal transition as a function of both LaAlO3and WO3layer thickness. Low-temperature magnetotransport reveals a strong magnetoresistance reaching 900% at 10 T and 1.5 K, the presence of multiple conduction channels with carrier mobility up to 80 000 cm2V-1s-1, and quantum oscillations of conductance.