Quantum oscillations in an optically-illuminated two-dimensional electron system at the LaAlO₃/SrTiO₃interface

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 (∼2 1012 cm-2) and effective mass (∼1.7m e) estimated from the oscillations suggest that the high-mobility electrons occupy the d xz/yz subbands of Ti:t2g 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.