Quantum oscillations in an optically-illuminated two-dimensional electron system at the LaAlO$_3$/SrTiO$_3$ interface

TL;DR

This study explores how optical illumination affects magnetotransport in a 2D electron system at the LaAlO₃/SrTiO₃ interface, revealing increased carrier density, quantum oscillations, and suppression of the Kondo effect, enabling better control of quantum transport.

Contribution

It demonstrates that illumination-induced carrier increase can control scattering mechanisms and reveal quantum oscillations in oxide interfaces, advancing understanding of complex oxide heterostructures.

Findings

Illumination reduces sheet resistance and eliminates the Kondo effect.

Quantum oscillations from Landau quantization are observed after illumination.

High-mobility carriers occupy Ti t₂g dₓz/yz subbands deep within the conducting sheet.

Abstract

We have investigated the illumination effect on the magnetotransport properties of a two-dimensional electron system at the LaAlO$_3$/SrTiO$_3$ 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 ($\sim 2 \times 10^{12}$ cm$^{-2}$) and effective mass ($\sim 1.7 ~m_e$) 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 SrTiO$_3$. 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.