Quantum oscillations in an optically-illuminated two-dimensional electron system at the LaAlO3/SrTiO3 interface

We have investigated the illumination effect on the magnetotransport properties of a two-dimensional electron system at the LaAlO3/SrTiO3 interface. The illumination significantly reduces the zero-field sheet resistance, eliminates the Kondo effect at low-temperature, and switches the negative magnetoresistance into the positive one. A large increase in the density of high-mobility carriers after illumination leads to quantum oscillations in the magnetoresistance originating from the Landau quantization. The carrier density (similar to 2 x 10(12) cm(-2)) and effective mass (similar to 1.7m (e)) estimated from the oscillations suggest that the high-mobility electrons occupy the d ( xz/yz ) subbands of Ti:t(2g ) orbital extending deep within the conducting sheet of SrTiO3. Our results demonstrate that the illumination which induces additional carriers at the interface can pave the way to control the Kondo-like scattering and study the quantum transport in the complex oxide heterostructures.