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/SrTiO₃interface. 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 thedsubbands of Ti:t₂orbital 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.